Optimize for TouchStart responsiveness

components/scheduler/renderer/renderer_scheduler.h

 // Copyright 2014 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.
 
 #ifndef COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_
 #define COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_
 
 #include "base/message_loop/message_loop.h"
 #include "components/scheduler/child/child_scheduler.h"
 #include "components/scheduler/child/single_thread_idle_task_runner.h"
 #include "components/scheduler/scheduler_export.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 
 namespace cc {
 struct BeginFrameArgs;
 }
 
 namespace scheduler {
 
 class SCHEDULER_EXPORT RendererScheduler : public ChildScheduler {
  public:
   ~RendererScheduler() override;
   static scoped_ptr<RendererScheduler> Create();
 
   // Returns the compositor task runner.
   virtual scoped_refptr<base::SingleThreadTaskRunner>
   CompositorTaskRunner() = 0;
 
+  // Keep RendererScheduler::UseCaseToString in sync with this enum.
+  enum class UseCase {
+    NONE,
+    COMPOSITOR_GESTURE,
+    MAIN_THREAD_GESTURE,
+    TOUCHSTART,
+    LOADING,
+    // Must be the last entry.
+    USE_CASE_COUNT,
+    FIRST_USE_CASE = NONE,
+  };
+  static const char* UseCaseToString(UseCase use_case);
+
   // Returns the loading task runner.  This queue is intended for tasks related
   // to resource dispatch, foreground HTML parsing, etc...
   virtual scoped_refptr<base::SingleThreadTaskRunner> LoadingTaskRunner() = 0;
 
   // Returns the timer task runner.  This queue is intended for DOM Timers.
   virtual scoped_refptr<TaskQueue> TimerTaskRunner() = 0;
 
   // Called to notify about the start of an extended period where no frames
   // need to be drawn. Must be called from the main thread.
   virtual void BeginFrameNotExpectedSoon() = 0;
 
   // Called to notify about the start of a new frame.  Must be called from the
   // main thread.
   virtual void WillBeginFrame(const cc::BeginFrameArgs& args) = 0;
 
   // Called to notify that a previously begun frame was committed. Must be
   // called from the main thread.
   virtual void DidCommitFrameToCompositor() = 0;
 
+  // Keep RendererScheduler::InputEventStateToString in sync with this enum.
   enum class InputEventState {
     EVENT_CONSUMED_BY_COMPOSITOR,
     EVENT_FORWARDED_TO_MAIN_THREAD,
   };
+  static const char* InputEventStateToString(InputEventState input_event_state);
 
   // Tells the scheduler that the system processed an input event. Called by the
   // compositor (impl) thread.  Note it's expected that every call to
   // DidHandleInputEventOnCompositorThread where |event_state| is
   // EVENT_FORWARDED_TO_MAIN_THREAD will be followed by a corresponding call
   // to DidHandleInputEventOnMainThread.
   virtual void DidHandleInputEventOnCompositorThread(
       const blink::WebInputEvent& web_input_event,
       InputEventState event_state) = 0;
 
@@ skipping 53 matching lines @@
   virtual void SetTimerQueueSuspensionWhenBackgroundedEnabled(bool enabled) = 0;
 
  protected:
   RendererScheduler();
   DISALLOW_COPY_AND_ASSIGN(RendererScheduler);
 };
 
 }  // namespace scheduler
 
 #endif  // COMPONENTS_SCHEDULER_RENDERER_RENDERER_SCHEDULER_H_