headless: Enable GL support by default

headless/lib/headless_content_main_delegate.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "headless/lib/headless_content_main_delegate.h"
 
 #include "base/command_line.h"
 #include "base/path_service.h"
 #include "base/run_loop.h"
 #include "base/trace_event/trace_event.h"
 #include "content/public/browser/browser_main_runner.h"
 #include "content/public/common/content_switches.h"
 #include "headless/lib/browser/headless_browser_impl.h"
 #include "headless/lib/browser/headless_content_browser_client.h"
 #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 {
 namespace {
 // Keep in sync with content/common/content_constants_internal.h.
 // TODO(skyostil): Add a tracing test for this.
 const int kTraceEventBrowserProcessSortIndex = -6;
 
 HeadlessContentMainDelegate* g_current_headless_content_main_delegate = nullptr;
 }  // namespace
@@ skipping 16 matching lines @@
   if (browser_->options()->single_process_mode)
     command_line->AppendSwitch(switches::kSingleProcess);
 
   if (browser_->options()->disable_sandbox)
     command_line->AppendSwitch(switches::kNoSandbox);
 
   // The headless backend is automatically chosen for a headless build, but also
   // 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;
 }
 
 void HeadlessContentMainDelegate::PreSandboxStartup() {
   InitializeResourceBundle();
 }
 
 int HeadlessContentMainDelegate::RunProcess(
@@ skipping 52 matching lines @@
   return renderer_client_.get();
 }
 
 content::ContentUtilityClient*
 HeadlessContentMainDelegate::CreateContentUtilityClient() {
   utility_client_.reset(new HeadlessContentUtilityClient);
   return utility_client_.get();
 }
 
 }  // namespace headless