headless: Enable GL support by default

Enable GL support by default so that WebGL and GL-based canvas rendering
can be used. GL support can still be disabled to save resources if
necessary.

BUG=617551

Review-Url: https://codereview.chromium.org/2184763002
Cr-Commit-Position: refs/heads/master@{#408121}

headless/DEPS

@@ -7,5 +7,6 @@ include_rules = [
   "+ui/display",
   "+ui/gfx",
   "+ui/gfx/geometry",
+  "+ui/gl",
   "+ui/ozone/public",
 ]

headless/lib/headless_browser_browsertest.cc

@@ -159,4 +159,19 @@ IN_PROC_BROWSER_TEST_F(HeadlessBrowserTest, HttpsProtocolHandler) {
   EXPECT_EQ(kResponseBody, inner_html);
 }
 
+IN_PROC_BROWSER_TEST_F(HeadlessBrowserTest, WebGLSupported) {
+  HeadlessWebContents* web_contents =
+      browser()->CreateWebContentsBuilder().Build();
+
+  bool webgl_supported;
+  EXPECT_TRUE(EvaluateScript(
+      web_contents,
+      "(document.createElement('canvas').getContext('webgl')"
+      "    instanceof WebGLRenderingContext)")
+                  ->GetResult()
+                  ->GetValue()
+                  ->GetAsBoolean(&webgl_supported));
+  EXPECT_TRUE(webgl_supported);
+}
+
 }  // namespace headless

headless/lib/headless_content_main_delegate.cc

@@ -15,6 +15,7 @@
 #include "headless/lib/renderer/headless_content_renderer_client.h"
 #include "headless/lib/utility/headless_content_utility_client.h"
 #include "ui/base/resource/resource_bundle.h"
+#include "ui/gl/gl_switches.h"
 #include "ui/ozone/public/ozone_switches.h"
 
 namespace headless {
@@ -51,8 +52,12 @@ bool HeadlessContentMainDelegate::BasicStartupComplete(int* exit_code) {
   // adding it here allows us to run in a non-headless build too.
   command_line->AppendSwitchASCII(switches::kOzonePlatform, "headless");
 
-  // TODO(skyostil): Investigate using Mesa/SwiftShader for output.
-  command_line->AppendSwitch(switches::kDisableGpu);
+  if (!browser_->options()->gl_implementation.empty()) {
+    command_line->AppendSwitchASCII(switches::kUseGL,
+                                    browser_->options()->gl_implementation);
+  } else {
+    command_line->AppendSwitch(switches::kDisableGpu);
+  }
 
   SetContentClient(&content_client_);
   return false;

headless/public/headless_browser.cc

@@ -21,7 +21,8 @@ Options::Options(int argc, const char** argv)
       user_agent(content::BuildUserAgentFromProduct(kProductName)),
       message_pump(nullptr),
       single_process_mode(false),
-      disable_sandbox(false) {}
+      disable_sandbox(false),
+      gl_implementation("osmesa") {}
 
 Options::Options(Options&& options) = default;
 
@@ -75,6 +76,11 @@ Builder& Builder::SetProtocolHandlers(ProtocolHandlerMap protocol_handlers) {
   return *this;
 }
 
+Builder& Builder::SetGLImplementation(const std::string& gl_implementation) {
+  options_.gl_implementation = gl_implementation;
+  return *this;
+}
+
 Options Builder::Build() {
   return std::move(options_);
 }

headless/public/headless_browser.h

@@ -121,6 +121,11 @@ struct HeadlessBrowser::Options {
   // fetching for different network schemes.
   ProtocolHandlerMap protocol_handlers;
 
+  // Choose the GL implementation to use for rendering. A suitable
+  // implementantion is selected by default. Setting this to an empty
+  // string can be used to disable GL rendering (e.g., WebGL support).
+  std::string gl_implementation;
+
  private:
   Options(int argc, const char** argv);
 
@@ -141,6 +146,7 @@ class HeadlessBrowser::Options::Builder {
   Builder& SetSingleProcessMode(bool single_process_mode);
   Builder& SetDisableSandbox(bool disable_sandbox);
   Builder& SetProtocolHandlers(ProtocolHandlerMap protocol_handlers);
+  Builder& SetGLImplementation(const std::string& gl_implementation);
 
   Options Build();