diff --git a/extensions/browser/api/web_request/form_data_parser.cc b/extensions/browser/api/web_request/form_data_parser.cc
index c2266ae84eb9db..45f1bf4b68d47e 100644
--- a/extensions/browser/api/web_request/form_data_parser.cc
+++ b/extensions/browser/api/web_request/form_data_parser.cc
@@ -12,6 +12,7 @@
 #include "base/lazy_instance.h"
 #include "base/notreached.h"
 #include "base/stl_util.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/values.h"
 #include "net/base/escape.h"
@@ -552,11 +553,11 @@ bool FormDataParserMultipart::GetNextNameValue(Result* result) {
   result->set_name(net::UnescapeBinaryURLComponent(name));
   if (value_assigned) {
     // Hold filename as value.
-    result->SetStringValue(value.as_string());
+    result->SetStringValue(std::string(value));
   } else if (value_is_binary) {
     result->SetBinaryValue(value);
   } else {
-    result->SetStringValue(value.as_string());
+    result->SetStringValue(std::string(value));
   }
 
   return return_value;
diff --git a/extensions/browser/url_request_util.cc b/extensions/browser/url_request_util.cc
index 8c032be21404f7..76fedd433d5e2f 100644
--- a/extensions/browser/url_request_util.cc
+++ b/extensions/browser/url_request_util.cc
@@ -6,6 +6,7 @@
 
 #include <string>
 
+#include "base/strings/string_piece.h"
 #include "extensions/browser/extension_navigation_ui_data.h"
 #include "extensions/browser/extensions_browser_client.h"
 #include "extensions/browser/guest_view/web_view/web_view_renderer_state.h"
@@ -102,7 +103,7 @@ bool AllowCrossRendererResourceLoad(
   // Allow web accessible extension resources to be loaded as
   // subresources/sub-frames.
   if (WebAccessibleResourcesInfo::IsResourceWebAccessible(
-          extension, resource_path.as_string(), request.request_initiator)) {
+          extension, std::string(resource_path), request.request_initiator)) {
     *allowed = true;
     return true;
   }
@@ -137,7 +138,7 @@ bool AllowCrossRendererResourceLoadHelper(bool is_guest,
     }
 
     *allowed = WebviewInfo::IsResourceWebviewAccessible(
-        extension, partition_id, resource_path.as_string());
+        extension, partition_id, std::string(resource_path));
     return true;
   }
 
diff --git a/extensions/common/csp_validator.cc b/extensions/common/csp_validator.cc
index de938624581237..4ccdf7de782866 100644
--- a/extensions/common/csp_validator.cc
+++ b/extensions/common/csp_validator.cc
@@ -255,17 +255,17 @@ std::string GetSecureDirectiveValues(
     if (is_secure_csp_token) {
       sane_csp_parts.push_back(source_literal);
     } else if (warnings) {
-      warnings->push_back(InstallWarning(
-          ErrorUtils::FormatErrorMessage(
-              manifest_errors::kInvalidCSPInsecureValueIgnored, manifest_key,
-              source_literal.as_string(), directive_name),
-          manifest_key));
+      warnings->push_back(
+          InstallWarning(ErrorUtils::FormatErrorMessage(
+                             manifest_errors::kInvalidCSPInsecureValueIgnored,
+                             manifest_key, source_literal, directive_name),
+                         manifest_key));
     }
   }
   // End of CSP directive that was started at the beginning of this method. If
   // none of the values are secure, the policy will be empty and default to
   // 'none', which is secure.
-  std::string last_part = sane_csp_parts.back().as_string();
+  std::string last_part(sane_csp_parts.back());
   last_part.push_back(kDirectiveSeparator);
   sane_csp_parts.back() = last_part;
   return base::JoinString(sane_csp_parts, " ");
@@ -293,11 +293,11 @@ std::string GetAppSandboxSecureDirectiveValues(
       seen_self_or_none |= source_lower == "'none'" || source_lower == "'self'";
       sane_csp_parts.push_back(source_lower);
     } else if (warnings) {
-      warnings->push_back(InstallWarning(
-          ErrorUtils::FormatErrorMessage(
-              manifest_errors::kInvalidCSPInsecureValueIgnored, manifest_key,
-              source_literal.as_string(), directive_name),
-          manifest_key));
+      warnings->push_back(
+          InstallWarning(ErrorUtils::FormatErrorMessage(
+                             manifest_errors::kInvalidCSPInsecureValueIgnored,
+                             manifest_key, source_literal, directive_name),
+                         manifest_key));
     }
   }
 
@@ -351,7 +351,7 @@ class CSPDirectiveToken {
     if (secure_value_)
       return secure_value_.value();
     // This token didn't require modification.
-    return directive_.directive_string.as_string() + kDirectiveSeparator;
+    return std::string(directive_.directive_string) + kDirectiveSeparator;
   }
 
  private:
diff --git a/extensions/common/csp_validator_unittest.cc b/extensions/common/csp_validator_unittest.cc
index 5646f5be5221ec..7eda0bae36e113 100644
--- a/extensions/common/csp_validator_unittest.cc
+++ b/extensions/common/csp_validator_unittest.cc
@@ -4,6 +4,7 @@
 
 #include <stddef.h>
 
+#include "base/strings/string_piece.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
@@ -544,7 +545,7 @@ namespace csp_validator {
 
 void PrintTo(const CSPParser::Directive& directive, ::std::ostream* os) {
   *os << base::StringPrintf(
-      "[[%s] [%s] [%s]]", directive.directive_string.as_string().c_str(),
+      "[[%s] [%s] [%s]]", std::string(directive.directive_string).c_str(),
       directive.directive_name.c_str(),
       base::JoinString(directive.directive_values, ",").c_str());
 }
diff --git a/extensions/common/error_utils.cc b/extensions/common/error_utils.cc
index 47e08ac1b2ea0b..fd5aef4563bf83 100644
--- a/extensions/common/error_utils.cc
+++ b/extensions/common/error_utils.cc
@@ -7,6 +7,7 @@
 #include <initializer_list>
 
 #include "base/check_op.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_tokenizer.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
@@ -18,7 +19,7 @@ namespace {
 std::string FormatErrorMessageInternal(
     base::StringPiece format,
     std::initializer_list<base::StringPiece> args) {
-  std::string format_str = format.as_string();
+  std::string format_str(format);
   base::StringTokenizer tokenizer(format_str, "*");
   tokenizer.set_options(base::StringTokenizer::RETURN_DELIMS);
 
diff --git a/extensions/common/extension_l10n_util.cc b/extensions/common/extension_l10n_util.cc
index 1a51563968520d..e60074987c9b60 100644
--- a/extensions/common/extension_l10n_util.cc
+++ b/extensions/common/extension_l10n_util.cc
@@ -17,6 +17,7 @@
 #include "base/json/json_string_value_serializer.h"
 #include "base/logging.h"
 #include "base/no_destructor.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
@@ -560,13 +561,13 @@ ScopedLocaleForTest::ScopedLocaleForTest(base::StringPiece locale)
 ScopedLocaleForTest::ScopedLocaleForTest(base::StringPiece process_locale,
                                          base::StringPiece preferred_locale)
     : ScopedLocaleForTest() {
-  SetProcessLocale(process_locale.as_string());
-  SetPreferredLocale(preferred_locale.as_string());
+  SetProcessLocale(std::string(process_locale));
+  SetPreferredLocale(std::string(preferred_locale));
 }
 
 ScopedLocaleForTest::~ScopedLocaleForTest() {
-  SetProcessLocale(process_locale_.as_string());
-  SetPreferredLocale(preferred_locale_.as_string());
+  SetProcessLocale(std::string(process_locale_));
+  SetPreferredLocale(std::string(preferred_locale_));
 }
 
 const std::string& GetPreferredLocaleForTest() {
diff --git a/extensions/common/features/feature.cc b/extensions/common/features/feature.cc
index e5a56080ec6f16..6c3795d493ce4f 100644
--- a/extensions/common/features/feature.cc
+++ b/extensions/common/features/feature.cc
@@ -8,6 +8,7 @@
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "build/build_config.h"
 #include "build/chromeos_buildflags.h"
@@ -48,15 +49,15 @@ Feature::Feature() : no_parent_(false) {}
 Feature::~Feature() {}
 
 void Feature::set_name(base::StringPiece name) {
-  name_ = name.as_string();
+  name_ = std::string(name);
 }
 
 void Feature::set_alias(base::StringPiece alias) {
-  alias_ = alias.as_string();
+  alias_ = std::string(alias);
 }
 
 void Feature::set_source(base::StringPiece source) {
-  source_ = source.as_string();
+  source_ = std::string(source);
 }
 
 }  // namespace extensions
diff --git a/extensions/common/features/feature_provider.cc b/extensions/common/features/feature_provider.cc
index bc017ec7cc57a8..4b749babe270c6 100644
--- a/extensions/common/features/feature_provider.cc
+++ b/extensions/common/features/feature_provider.cc
@@ -11,7 +11,9 @@
 #include "base/debug/alias.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
+#include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/trace_event/trace_event.h"
@@ -196,11 +198,11 @@ const FeatureMap& FeatureProvider::GetAllFeatures() const {
 
 void FeatureProvider::AddFeature(base::StringPiece name,
                                  std::unique_ptr<Feature> feature) {
-  features_[name.as_string()] = std::move(feature);
+  features_[std::string(name)] = std::move(feature);
 }
 
 void FeatureProvider::AddFeature(base::StringPiece name, Feature* feature) {
-  features_[name.as_string()] = std::unique_ptr<Feature>(feature);
+  features_[std::string(name)] = base::WrapUnique(feature);
 }
 
 }  // namespace extensions
diff --git a/extensions/common/features/simple_feature.cc b/extensions/common/features/simple_feature.cc
index 5f63558d917817..8e97b87695ba24 100644
--- a/extensions/common/features/simple_feature.cc
+++ b/extensions/common/features/simple_feature.cc
@@ -14,6 +14,7 @@
 #include "base/containers/contains.h"
 #include "base/macros.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "components/crx_file/id_util.h"
@@ -531,7 +532,7 @@ void SimpleFeature::set_blocklist(
 
 void SimpleFeature::set_command_line_switch(
     base::StringPiece command_line_switch) {
-  command_line_switch_ = command_line_switch.as_string();
+  command_line_switch_ = std::string(command_line_switch);
 }
 
 void SimpleFeature::set_contexts(std::initializer_list<Context> contexts) {
@@ -549,7 +550,7 @@ void SimpleFeature::set_extension_types(
 }
 
 void SimpleFeature::set_feature_flag(base::StringPiece feature_flag) {
-  feature_flag_ = feature_flag.as_string();
+  feature_flag_ = std::string(feature_flag);
 }
 
 void SimpleFeature::set_session_types(
diff --git a/extensions/common/manifest_handlers/csp_info.cc b/extensions/common/manifest_handlers/csp_info.cc
index 1b06d06cec875a..209c373f5e9f44 100644
--- a/extensions/common/manifest_handlers/csp_info.cc
+++ b/extensions/common/manifest_handlers/csp_info.cc
@@ -8,6 +8,7 @@
 #include <utility>
 
 #include "base/no_destructor.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
@@ -253,7 +254,7 @@ bool CSPHandler::ParseExtensionPagesCSP(
 
   std::vector<InstallWarning> warnings;
   std::string sanitized_content_security_policy = SanitizeContentSecurityPolicy(
-      content_security_policy_str, manifest_key.as_string(),
+      content_security_policy_str, std::string(manifest_key),
       GetValidatorOptions(extension), &warnings);
   extension->AddInstallWarnings(std::move(warnings));
 
@@ -287,7 +288,7 @@ bool CSPHandler::ParseSandboxCSP(Extension* extension,
   std::vector<InstallWarning> warnings;
   std::string effective_sandbox_csp =
       csp_validator::GetEffectiveSandoxedPageCSP(
-          sandbox_csp_str, manifest_key.as_string(), &warnings);
+          sandbox_csp_str, std::string(manifest_key), &warnings);
   SetSandboxCSP(extension, std::move(effective_sandbox_csp));
   extension->AddInstallWarnings(std::move(warnings));
   return true;
@@ -304,7 +305,7 @@ bool CSPHandler::SetExtensionPagesCSP(Extension* extension,
   } else {
     DCHECK_EQ(content_security_policy,
               SanitizeContentSecurityPolicy(
-                  content_security_policy, manifest_key.as_string(),
+                  content_security_policy, std::string(manifest_key),
                   GetValidatorOptions(extension), nullptr));
   }
 
diff --git a/extensions/common/manifest_test.cc b/extensions/common/manifest_test.cc
index 25f89d81fed901..1cbbe09a75ccdb 100644
--- a/extensions/common/manifest_test.cc
+++ b/extensions/common/manifest_test.cc
@@ -11,6 +11,7 @@
 #include "base/json/json_file_value_serializer.h"
 #include "base/path_service.h"
 #include "base/strings/pattern.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/values.h"
@@ -67,11 +68,11 @@ ManifestTest::~ManifestTest() {
 // Helper class that simplifies creating methods that take either a filename
 // to a manifest or the manifest itself.
 ManifestTest::ManifestData::ManifestData(base::StringPiece name)
-    : name_(name.as_string()) {}
+    : name_(name) {}
 
 ManifestTest::ManifestData::ManifestData(base::Value manifest,
                                          base::StringPiece name)
-    : name_(name.as_string()), manifest_(std::move(manifest)) {
+    : name_(name), manifest_(std::move(manifest)) {
   CHECK(manifest_.is_dict()) << "Manifest must be a dictionary. " << name_;
 }
 
diff --git a/extensions/common/url_pattern.cc b/extensions/common/url_pattern.cc
index aa9bfb116af43c..00f949506602c0 100644
--- a/extensions/common/url_pattern.cc
+++ b/extensions/common/url_pattern.cc
@@ -12,6 +12,7 @@
 #include "base/strings/pattern.h"
 #include "base/strings/strcat.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
@@ -308,7 +309,7 @@ URLPattern::ParseResult URLPattern::Parse(base::StringPiece pattern) {
       host_piece = host_piece.substr(2);
     }
 
-    host_ = host_piece.as_string();
+    host_ = std::string(host_piece);
 
     path_start_pos = host_end_pos;
   }
diff --git a/extensions/renderer/bindings/api_binding_hooks_test_delegate.cc b/extensions/renderer/bindings/api_binding_hooks_test_delegate.cc
index a175c703e6e903..77a8a2bef7721b 100644
--- a/extensions/renderer/bindings/api_binding_hooks_test_delegate.cc
+++ b/extensions/renderer/bindings/api_binding_hooks_test_delegate.cc
@@ -4,6 +4,8 @@
 
 #include "extensions/renderer/bindings/api_binding_hooks_test_delegate.h"
 
+#include "base/strings/string_piece.h"
+
 namespace extensions {
 
 APIBindingHooksTestDelegate::APIBindingHooksTestDelegate() {}
@@ -22,7 +24,7 @@ bool APIBindingHooksTestDelegate::CreateCustomEvent(
 
 void APIBindingHooksTestDelegate::AddHandler(base::StringPiece name,
                                              RequestHandler handler) {
-  request_handlers_[name.as_string()] = std::move(handler);
+  request_handlers_[std::string(name)] = std::move(handler);
 }
 
 void APIBindingHooksTestDelegate::SetCustomEvent(
diff --git a/extensions/renderer/bindings/api_binding_test_util.cc b/extensions/renderer/bindings/api_binding_test_util.cc
index 073e572e5d492e..d3fff7d03971db 100644
--- a/extensions/renderer/bindings/api_binding_test_util.cc
+++ b/extensions/renderer/bindings/api_binding_test_util.cc
@@ -6,6 +6,7 @@
 
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "base/values.h"
 #include "content/public/renderer/v8_value_converter.h"
@@ -49,7 +50,7 @@ bool RunFunctionImpl(v8::Local<v8::Function> function,
 
 std::string ReplaceSingleQuotes(base::StringPiece str) {
   std::string result;
-  base::ReplaceChars(str.as_string(), "'", "\"", &result);
+  base::ReplaceChars(str, "'", "\"", &result);
   return result;
 }
 
diff --git a/extensions/renderer/bindings/argument_spec.h b/extensions/renderer/bindings/argument_spec.h
index ababad6b1879f5..8abc4217d8b1a9 100644
--- a/extensions/renderer/bindings/argument_spec.h
+++ b/extensions/renderer/bindings/argument_spec.h
@@ -83,9 +83,9 @@ class ArgumentSpec {
   ArgumentType type() const { return type_; }
   const std::set<std::string>& enum_values() const { return enum_values_; }
 
-  void set_name(base::StringPiece name) { name_ = name.as_string(); }
+  void set_name(base::StringPiece name) { name_ = std::string(name); }
   void set_optional(bool optional) { optional_ = optional; }
-  void set_ref(base::StringPiece ref) { ref_ = ref.as_string(); }
+  void set_ref(base::StringPiece ref) { ref_ = std::string(ref); }
   void set_minimum(int minimum) { minimum_ = minimum; }
   void set_properties(PropertiesMap properties) {
     properties_ = std::move(properties);
diff --git a/extensions/renderer/bindings/argument_spec_builder.cc b/extensions/renderer/bindings/argument_spec_builder.cc
index a12cdeb7a5afa1..6bd0d0e14019a7 100644
--- a/extensions/renderer/bindings/argument_spec_builder.cc
+++ b/extensions/renderer/bindings/argument_spec_builder.cc
@@ -4,6 +4,7 @@
 
 #include "extensions/renderer/bindings/argument_spec_builder.h"
 
+#include "base/strings/string_piece.h"
 
 namespace extensions {
 
@@ -27,7 +28,7 @@ ArgumentSpecBuilder& ArgumentSpecBuilder::MakeOptional() {
 ArgumentSpecBuilder& ArgumentSpecBuilder::AddProperty(
     base::StringPiece property_name,
     std::unique_ptr<ArgumentSpec> property_spec) {
-  properties_[property_name.as_string()] = std::move(property_spec);
+  properties_[std::string(property_name)] = std::move(property_spec);
   return *this;
 }
 
diff --git a/extensions/renderer/content_watcher.cc b/extensions/renderer/content_watcher.cc
index 7e6c3ddda73d32..55961162fd1874 100644
--- a/extensions/renderer/content_watcher.cc
+++ b/extensions/renderer/content_watcher.cc
@@ -8,6 +8,7 @@
 
 #include <set>
 
+#include "base/strings/string_piece.h"
 #include "content/public/renderer/render_frame.h"
 #include "content/public/renderer/render_frame_observer.h"
 #include "content/public/renderer/render_frame_observer_tracker.h"
@@ -129,7 +130,7 @@ void FrameContentWatcher::NotifyBrowserOfChange() {
 
   std::vector<std::string> selector_strings;
   for (const base::StringPiece& selector : transitive_selectors)
-    selector_strings.push_back(selector.as_string());
+    selector_strings.push_back(std::string(selector));
 
   ExtensionFrameHelper::Get(render_frame())
       ->GetLocalFrameHost()
diff --git a/extensions/renderer/native_extension_bindings_system.cc b/extensions/renderer/native_extension_bindings_system.cc
index 6b3f5e48aa7f0b..f7226c51c696ec 100644
--- a/extensions/renderer/native_extension_bindings_system.cc
+++ b/extensions/renderer/native_extension_bindings_system.cc
@@ -8,6 +8,7 @@
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/strings/string_piece.h"
 #include "base/timer/elapsed_timer.h"
 #include "components/crx_file/id_util.h"
 #include "content/public/common/content_switches.h"
@@ -320,7 +321,7 @@ v8::Local<v8::Object> CreateFullBinding(
 
     v8::Local<v8::Object> nested_binding =
         CreateFullBinding(context, script_context, bindings_system,
-                          api_feature_provider, binding_name.as_string());
+                          api_feature_provider, std::string(binding_name));
     // It's possible that we don't create a binding if no features or
     // prefixed features are available to the context.
     if (nested_binding.IsEmpty())