Make disable vsync run the renderer independently

content/renderer/render_thread_impl.cc

 // Copyright (c) 2012 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 "content/renderer/render_thread_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <utility>
@@ skipping 144 matching lines @@
 #include "third_party/WebKit/public/web/WebKit.h"
 #include "third_party/WebKit/public/web/WebNetworkStateNotifier.h"
 #include "third_party/WebKit/public/web/WebRuntimeFeatures.h"
 #include "third_party/WebKit/public/web/WebScriptController.h"
 #include "third_party/WebKit/public/web/WebSecurityPolicy.h"
 #include "third_party/WebKit/public/web/WebView.h"
 #include "third_party/icu/source/i18n/unicode/timezone.h"
 #include "third_party/skia/include/core/SkGraphics.h"
 #include "ui/base/layout.h"
 #include "ui/base/ui_base_switches.h"
+#include "ui/gl/gl_switches.h"
 
 #if defined(OS_ANDROID)
 #include <cpu-features.h>
 #include "content/renderer/android/synchronous_compositor_filter.h"
 #include "content/renderer/android/synchronous_compositor_output_surface.h"
 #include "content/renderer/media/android/renderer_demuxer_android.h"
 #include "content/renderer/media/android/stream_texture_factory.h"
 #include "media/base/android/media_codec_util.h"
 #endif
 
@@ skipping 1412 matching lines @@
 #endif
   return  gpu_memory_buffer_manager();
 }
 
 blink::scheduler::RendererScheduler* RenderThreadImpl::GetRendererScheduler() {
   return renderer_scheduler_.get();
 }
 
 std::unique_ptr<cc::BeginFrameSource>
 RenderThreadImpl::CreateExternalBeginFrameSource(int routing_id) {
+  const base::CommandLine* cmd = base::CommandLine::ForCurrentProcess();
+  if (cmd->HasSwitch(switches::kDisableGpuVsync)) {
+    std::string display_vsync_string =
+        cmd->GetSwitchValueASCII(switches::kDisableGpuVsync);
+    if (display_vsync_string != "gpu") {
+      // In disable gpu vsync mode, also let the renderer tick as fast as it
+      // can.  The top level begin frame source will also be running as a back
+      // to back begin frame source, but using a synthetic begin frame source
+      // here reduces latency when in this mode (at least for frames
+      // starting--it potentially increases it for input on the other hand.)
+      base::SingleThreadTaskRunner* compositor_impl_side_task_runner =
+          compositor_task_runner_ ? compositor_task_runner_.get()
+                                  : base::ThreadTaskRunnerHandle::Get().get();
+      return base::MakeUnique<cc::BackToBackBeginFrameSource>(
+          base::MakeUnique<cc::DelayBasedTimeSource>(
+              compositor_impl_side_task_runner));
+    }
+  }
+
   return base::MakeUnique<CompositorExternalBeginFrameSource>(
       compositor_message_filter_.get(), sync_message_filter(), routing_id);
 }
 
 cc::ImageSerializationProcessor*
 RenderThreadImpl::GetImageSerializationProcessor() {
   return GetContentClient()->renderer()->GetImageSerializationProcessor();
 }
 
 cc::TaskGraphRunner* RenderThreadImpl::GetTaskGraphRunner() {
@@ skipping 643 matching lines @@
   if (blink::mainThreadIsolate()) {
     blink::mainThreadIsolate()->MemoryPressureNotification(
         v8::MemoryPressureLevel::kCritical);
     blink::MemoryPressureNotificationToWorkerThreadIsolates(
         v8::MemoryPressureLevel::kCritical);
   }
 }
 
 
 }  // namespace content