Mac: move content::RenderWidgetResizeHelper to ui::WindowResizeHelperMac (acelerated_widget_mac)

content/browser/renderer_host/render_widget_resize_helper_mac.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 CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_RESIZE_HELPER_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_RESIZE_HELPER_MAC_H_
 
-#include "base/lazy_instance.h"
-#include "base/single_thread_task_runner.h"
-#include "base/synchronization/lock.h"
-#include "base/synchronization/waitable_event.h"
-#include "ipc/ipc_message.h"
+#include "base/macros.h"
+
+namespace IPC {
+class Message;
+}
 
 namespace content {
 
-// RenderWidgetResizeHelper is used to make resize appear smooth. That is to
-// say, make sure that the window size and the size of the content being drawn
-// in that window are resized in lock-step. This is accomplished by waiting
-// inside -[RenderWidgetHostViewCocoa setFrameSize:] for the renderer (and
-// potentially browser compositor as well) to produce a frame of same size
-// as the RenderWidgetHostViewCocoa.
+// Provides functions for content to synchronize with window resize tasks being
+// managed by ui::WindowResizeHelperMac. WindowResizeHelperMac must be
+// initialized before calling these functions.
 //
-// The function of waiting for a frame of the correct size is done inside
-// RenderWidgetHostImpl::WaitForSurface. That function will call
-// RenderWidgetResizeHelper::WaitForSingleTaskToRun until a timeout occurs,
-// or the corresponding RenderWidgetHostViewCocoa has a renderer frame of the
-// same size as its NSView.
-//
-// This is somewhat complicated because waiting for frames requires that
-// that the browser handle the IPCs (from the renderer and the GPU processes)
-// that are required to pick up a new frame. In the ordinary run of things
-// (ignoring RenderWidgetResizeHelper), those IPCs arrive on the IO thread
+// The IPCs that are required to create new frames for smooth resize are sent
+// to the ui::WindowResizeHelperMac singleton using the PostRendererProcessMsg()
+// and PostGpuProcessMsg() methods. Usually those IPCs arrive on the IO thread
 // and are posted as tasks to the UI thread either by the RenderMessageFilter
 // (for renderer processes) or the GpuProcessHostUIShim (for the GPU process).
-// The IPCs that are required to create new frames for smooth resize are sent
-// to the RenderWidgetResizeHelper using the PostRendererProcessMsg and
-// PostGpuProcessMsg methods. These functions will post them as tasks to the UI
-// thread (as usual), and will also enqueue them into a queue which will be
-// read and run in RenderWidgetResizeHelper::WaitForSingleTaskToRun, potentially
-// before the task posted to the UI thread is run. Some care is taken (see
-// WrappedTask) to make sure that the messages are only executed once.
-//
-// This is further complicated because, in order for a frame to appear, it is
-// necessary to run tasks posted by the ui::Compositor. To accomplish this, the
-// RenderWidgetResizeHelper provides a base::SingleThreadTaskRunner which,
-// when a task is posted to it, enqueues the task in the aforementioned queue,
-// which may be pumped by RenderWidgetResizeHelper::WaitForSingleTaskToRun.
-//
+// By posting them via RenderWidgetResizeHelper instead, it allows a smooth
+// window resize to be controlled by WindowResizeHelperMac.
 class RenderWidgetResizeHelper {
  public:
-  static RenderWidgetResizeHelper* Get();
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner() const;
-
-  // UI THREAD ONLY -----------------------------------------------------------
-
-  // Waits at most |max_delay| for a task to run. Returns true if a task ran,
-  // false if no task ran.
-  bool WaitForSingleTaskToRun(const base::TimeDelta& max_delay);
-
   // IO THREAD ONLY -----------------------------------------------------------
 
   // This will cause |msg| to be handled by the RenderProcessHost corresponding
   // to |render_process_id|, on the UI thread. This will either happen when the
   // ordinary message loop would run it, or potentially earlier in a call to
-  // WaitForSingleTaskToRun .
-  void PostRendererProcessMsg(int render_process_id, const IPC::Message& msg);
+  // WindowResizeHelperMac::WaitForSingleTaskToRun().
+  static void PostRendererProcessMsg(int render_process_id,
+                                     const IPC::Message& msg);
 
   // This is similar to PostRendererProcessMsg, but will handle the message in
   // the GpuProcessHostUIShim corresponding to |gpu_host_id|.
-  void PostGpuProcessMsg(int gpu_host_id, const IPC::Message& msg);
+  static void PostGpuProcessMsg(int gpu_host_id, const IPC::Message& msg);
 
  private:
-  friend struct base::DefaultLazyInstanceTraits<RenderWidgetResizeHelper>;
-  RenderWidgetResizeHelper();
-  ~RenderWidgetResizeHelper();
-
-  // This helper is needed to create a ScopedAllowWait inside the scope of a
-  // class where it is allowed.
-  static void EventTimedWait(base::WaitableEvent* event, base::TimeDelta delay);
-
-  // The task runner to which the helper will post tasks. This also maintains
-  // the task queue and does the actual work for WaitForSingleTaskToRun.
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
-
-  DISALLOW_COPY_AND_ASSIGN(RenderWidgetResizeHelper);
+  DISALLOW_IMPLICIT_CONSTRUCTORS(RenderWidgetResizeHelper);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_RESIZE_HELPER_MAC_H_