gpu: Optimize in-process idle task scheduling

gpu/command_buffer/service/in_process_command_buffer.cc

Index: gpu/command_buffer/service/in_process_command_buffer.cc
diff --git a/gpu/command_buffer/service/in_process_command_buffer.cc b/gpu/command_buffer/service/in_process_command_buffer.cc
index c3123457f64ff1c42bbffcef368c49d86ba3f149..7f4276f027731a259b2cf7b8e2f7e09b76475297 100644
--- a/gpu/command_buffer/service/in_process_command_buffer.cc
+++ b/gpu/command_buffer/service/in_process_command_buffer.cc
@@ -82,13 +82,22 @@ class GpuInProcessThread
 
  private:
   ~GpuInProcessThread() override;
+
+  void CheckIdleTasksLocked();
+  void RunIdleTask();
+
   friend class base::RefCountedThreadSafe<GpuInProcessThread>;
 
   scoped_refptr<gpu::gles2::ShaderTranslatorCache> shader_translator_cache_;
+
+  base::Lock lock_;
+  bool idle_post_pending_;
+  std::queue<base::Closure> pending_idle_tasks_;
   DISALLOW_COPY_AND_ASSIGN(GpuInProcessThread);
 };
 
-GpuInProcessThread::GpuInProcessThread() : base::Thread("GpuThread") {
+GpuInProcessThread::GpuInProcessThread()
+    : base::Thread("GpuThread"), idle_post_pending_(false) {
   Start();
 }
 
@@ -101,8 +110,34 @@ void GpuInProcessThread::ScheduleTask(const base::Closure& task) {
 }
 
 void GpuInProcessThread::ScheduleIdleWork(const base::Closure& callback) {
-  message_loop()->PostDelayedTask(
-      FROM_HERE, callback, base::TimeDelta::FromMilliseconds(5));
+  base::AutoLock lock(lock_);
+  pending_idle_tasks_.push(callback);
+  CheckIdleTasksLocked();
+}
+
+void GpuInProcessThread::CheckIdleTasksLocked() {
+  lock_.AssertAcquired();
+  if (pending_idle_tasks_.size() && !idle_post_pending_) {
+    idle_post_pending_ = true;
+    message_loop()->PostTask(
+        FROM_HERE, base::Bind(&GpuInProcessThread::RunIdleTask, this));
+  }
+}
+
+void GpuInProcessThread::RunIdleTask() {
+  base::Closure idle_task;
+  base::AutoLock lock(lock_);
+  idle_post_pending_ = false;
+  DCHECK(pending_idle_tasks_.size());
+  idle_task = pending_idle_tasks_.front();
+  pending_idle_tasks_.pop();
+
+  {
+    base::AutoUnlock unlock(lock_);
+    idle_task.Run();
+  }
+
+  CheckIdleTasksLocked();
 }
 
 scoped_refptr<gles2::ShaderTranslatorCache>