Remove Cache Transparency implementation from //net

Remove Cache Transparency code from net::HttpCache::Transaction and
related classes.

Remove the histograms.xml entries for histograms that have been removed.

Remove CacheTransparencyNavigationBrowserTest.* and
URLLoaderCacheTransparencyTest.Redirect tests as they depend on
histograms that no longer exist. Remove files used by the browser tests.

Other parts of the cache transparency implementation outside //net still
remain.

OBSOLETE_HISTOGRAMS=Removed along with Cache Transparency implementation
BUG=1466829

Change-Id: I7a976bca695d6508ebceb944ed01e54d5db09031
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4707374
Reviewed-by: Takashi Toyoshima <toyoshim@chromium.org>
Commit-Queue: Adam Rice <ricea@chromium.org>
Reviewed-by: Rakina Zata Amni <rakina@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1174065}

content/browser/navigation_browsertest.cc

@@ -6995,64 +6995,6 @@ IN_PROC_BROWSER_TEST_F(NavigationBrowserTest,
   EXPECT_FALSE(site_instance->GetProcess()->IsUnused());
 }
 
-class CacheTransparencyNavigationBrowserTest : public ContentBrowserTest {
- public:
-  CacheTransparencyNavigationBrowserTest() {
-    EXPECT_TRUE(embedded_test_server()->Start());
-
-    pervasive_payload_url_ = embedded_test_server()->GetURL(kPervasivePayload);
-    std::string pervasive_payloads_params = base::StrCat(
-        {"1,", pervasive_payload_url_.spec(),
-         ",2478392C652868C0AAF0316A28284610DBDACF02D66A00B39F3BA75D887F4829"});
-
-    feature_list_.InitWithFeaturesAndParameters(
-        {{network::features::kPervasivePayloadsList,
-          {{"pervasive-payloads", pervasive_payloads_params}}},
-         {network::features::kCacheTransparency, {}},
-         {net::features::kSplitCacheByNetworkIsolationKey, {}}},
-        {/* disabled_features */});
-    ForceInProcessNetworkService();
-  }
-
-  void ExpectCacheUsed() const {
-    histogram_tester_.ExpectUniqueSample(kCacheUsedHistogram, 0, 1);
-  }
-
-  void ExpectCacheNotUsed() const {
-    histogram_tester_.ExpectTotalCount(kCacheUsedHistogram, 0);
-  }
-
- private:
-  static constexpr char kPervasivePayload[] =
-      "/cache_transparency/pervasive.js";
-  static constexpr char kCacheUsedHistogram[] =
-      "Network.CacheTransparency2.SingleKeyedCacheIsUsed";
-
-  base::test::ScopedFeatureList feature_list_;
-  GURL pervasive_payload_url_;
-  base::HistogramTester histogram_tester_;
-};
-
-IN_PROC_BROWSER_TEST_F(CacheTransparencyNavigationBrowserTest,
-                       SuccessfulPervasivePayload) {
-  GURL url_main_document =
-      embedded_test_server()->GetURL("/cache_transparency/pervasive.html");
-
-  EXPECT_TRUE(NavigateToURL(shell(), url_main_document));
-
-  ExpectCacheUsed();
-}
-
-IN_PROC_BROWSER_TEST_F(CacheTransparencyNavigationBrowserTest,
-                       NotAPervasivePayload) {
-  GURL url_main_document =
-      embedded_test_server()->GetURL("/cache_transparency/cacheable.html");
-
-  EXPECT_TRUE(NavigateToURL(shell(), url_main_document));
-
-  ExpectCacheNotUsed();
-}
-
 class NavigationBrowserTestWarnSandboxIneffective
     : public NavigationBrowserTest {
  public:

content/test/content_test_bundle_data.filelist

@@ -5296,11 +5296,9 @@ data/cache_storage/storage_key/0430f1a484a0ea6d8de562488c5fbeec0111d16f/ba31f73b
 data/cache_storage/storage_key/0430f1a484a0ea6d8de562488c5fbeec0111d16f/ba31f73b-95e8-44fb-a273-265e7e76f5ab/index
 data/cache_storage/storage_key/0430f1a484a0ea6d8de562488c5fbeec0111d16f/ba31f73b-95e8-44fb-a273-265e7e76f5ab/index-dir/the-real-index
 data/cache_storage/storage_key/0430f1a484a0ea6d8de562488c5fbeec0111d16f/index.txt
-data/cache_transparency/cacheable.html
 data/cache_transparency/cacheable.js
 data/cache_transparency/cacheable.js.mock-http-headers
 data/cache_transparency/cacheable2.html
-data/cache_transparency/pervasive.html
 data/cache_transparency/pervasive.js
 data/cache_transparency/pervasive.js.mock-http-headers
 data/cache_transparency/pervasive2.html

net/http/http_cache.cc

@@ -69,8 +69,6 @@ bool g_enable_split_cache = false;
 const char HttpCache::kDoubleKeyPrefix[] = "_dk_";
 const char HttpCache::kDoubleKeySeparator[] = " ";
 const char HttpCache::kSubframeDocumentResourcePrefix[] = "s_";
-const char HttpCache::kSingleKeyPrefix[] = "_sk_";
-const char HttpCache::kSingleKeySeparator[] = " ";
 
 HttpCache::DefaultBackend::DefaultBackend(
     CacheType type,
@@ -366,8 +364,7 @@ void HttpCache::OnExternalCacheHit(
       request_info.load_flags |= ~LOAD_DO_NOT_SAVE_COOKIES;
   }
 
-  std::string key = *GenerateCacheKeyForRequest(
-      &request_info, /*use_single_keyed_cache=*/false);
+  std::string key = *GenerateCacheKeyForRequest(&request_info);
   disk_cache_->OnExternalCacheHit(key);
 }
 
@@ -439,11 +436,6 @@ std::string HttpCache::GetResourceURLFromHttpCacheKey(const std::string& key) {
     DCHECK_NE(pos, std::string::npos);
     pos += strlen(kDoubleKeySeparator);
     DCHECK_LE(pos, key.size() - 1);
-  } else if (pos == key.find(kSingleKeyPrefix, pos)) {
-    pos = key.rfind(kSingleKeySeparator);
-    DCHECK_NE(pos, std::string::npos);
-    pos += strlen(kSingleKeySeparator);
-    DCHECK_LE(pos, key.size() - 1);
   }
   return key.substr(pos);
 }
@@ -455,32 +447,18 @@ absl::optional<std::string> HttpCache::GenerateCacheKey(
     int load_flags,
     const NetworkIsolationKey& network_isolation_key,
     int64_t upload_data_identifier,
-    bool is_subframe_document_resource,
-    bool use_single_keyed_cache,
-    const std::string& single_key_checksum) {
+    bool is_subframe_document_resource) {
   // The first character of the key may vary depending on whether or not sending
   // credentials is permitted for this request. This only happens if the
-  // SplitCacheByIncludeCredentials feature is enabled, or if the single-keyed
-  // cache is enabled. The single-keyed cache must always be split by
-  // credentials in order to make coep:credentialless work safely.
-  const char credential_key =
-      ((base::FeatureList::IsEnabled(
-            features::kSplitCacheByIncludeCredentials) ||
-        use_single_keyed_cache) &&
-       (load_flags & LOAD_DO_NOT_SAVE_COOKIES))
-          ? '0'
-          : '1';
+  // SplitCacheByIncludeCredentials feature is enabled.
+  const char credential_key = (base::FeatureList::IsEnabled(
+                                   features::kSplitCacheByIncludeCredentials) &&
+                               (load_flags & LOAD_DO_NOT_SAVE_COOKIES))
+                                  ? '0'
+                                  : '1';
 
   std::string isolation_key;
-  if (use_single_keyed_cache) {
-    DCHECK(IsSplitCacheEnabled());
-    DCHECK(!(load_flags &
-             (net::LOAD_VALIDATE_CACHE | net::LOAD_BYPASS_CACHE |
-              net::LOAD_SKIP_CACHE_VALIDATION | net::LOAD_ONLY_FROM_CACHE |
-              net::LOAD_DISABLE_CACHE | net::LOAD_SKIP_VARY_CHECK)));
-    isolation_key = base::StrCat(
-        {kSingleKeyPrefix, single_key_checksum, kSingleKeySeparator});
-  } else if (IsSplitCacheEnabled()) {
+  if (IsSplitCacheEnabled()) {
     // Prepend the key with |kDoubleKeyPrefix| = "_dk_" to mark it as
     // double-keyed (and makes it an invalid url so that it doesn't get
     // confused with a single-keyed entry). Separate the origin and url
@@ -507,16 +485,14 @@ absl::optional<std::string> HttpCache::GenerateCacheKey(
 
 // static
 absl::optional<std::string> HttpCache::GenerateCacheKeyForRequest(
-    const HttpRequestInfo* request,
-    bool use_single_keyed_cache) {
+    const HttpRequestInfo* request) {
   DCHECK(request);
   const int64_t upload_data_identifier =
       request->upload_data_stream ? request->upload_data_stream->identifier()
                                   : int64_t(0);
   return GenerateCacheKey(
       request->url, request->load_flags, request->network_isolation_key,
-      upload_data_identifier, request->is_subframe_document_resource,
-      use_single_keyed_cache, request->checksum);
+      upload_data_identifier, request->is_subframe_document_resource);
 }
 
 // static
@@ -694,11 +670,7 @@ void HttpCache::DoomMainEntryForUrl(const GURL& url,
       net::NetworkAnonymizationKey::CreateFromNetworkIsolationKey(
           isolation_key);
   temp_info.is_subframe_document_resource = is_subframe_document_resource;
-  // This method is always used for "POST" requests, which never use the
-  // single-keyed cache, so therefore it is correct that use_single_keyed_cache
-  // be false.
-  std::string key =
-      *GenerateCacheKeyForRequest(&temp_info, /*use_single_keyed_cache=*/false);
+  std::string key = *GenerateCacheKeyForRequest(&temp_info);
 
   // Defer to DoomEntry if there is an active entry, otherwise call
   // AsyncDoomEntry without triggering a callback.

net/http/http_cache.h

@@ -265,12 +265,9 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory {
       int load_flags,
       const NetworkIsolationKey& network_isolation_key,
       int64_t upload_data_identifier,
-      bool is_subframe_document_resource,
-      bool use_single_keyed_cache,
-      const std::string& single_key_checksum);
+      bool is_subframe_document_resource);
   static absl::optional<std::string> GenerateCacheKeyForRequest(
-      const HttpRequestInfo* request,
-      bool use_single_keyed_cache = false);
+      const HttpRequestInfo* request);
 
   // Enable split cache feature if not already overridden in the feature list.
   // Should only be invoked during process initialization before the HTTP