Mac Overlays: Add GPU back-pressure

content/common/gpu/image_transport_surface_overlay_mac.h

Index: content/common/gpu/image_transport_surface_overlay_mac.h
diff --git a/content/common/gpu/image_transport_surface_overlay_mac.h b/content/common/gpu/image_transport_surface_overlay_mac.h
index 66c0591f1ee365618d667be13d0aaefe99e5d24a..022fbb41e7922a9c8e607529348033b12842f3c0 100644
--- a/content/common/gpu/image_transport_surface_overlay_mac.h
+++ b/content/common/gpu/image_transport_surface_overlay_mac.h
@@ -5,9 +5,13 @@
 #ifndef CONTENT_COMMON_GPU_IMAGE_TRANSPORT_SURFACE_OVERLAY_MAC_H_
 #define CONTENT_COMMON_GPU_IMAGE_TRANSPORT_SURFACE_OVERLAY_MAC_H_
 
+#include <deque>
+
+#include "base/memory/linked_ptr.h"
 #import "base/mac/scoped_nsobject.h"
 #include "content/common/gpu/gpu_command_buffer_stub.h"
 #include "content/common/gpu/image_transport_surface.h"
+#include "ui/accelerated_widget_mac/display_link_mac.h"
 #include "ui/gl/gl_surface.h"
 
 @class CAContext;
@@ -47,14 +51,35 @@ class ImageTransportSurfaceOverlayMac : public gfx::GLSurface,
   void WakeUpGpu() override;
 
  private:
+  class PendingSwap;
+
   ~ImageTransportSurfaceOverlayMac() override;
+
+  gfx::SwapResult SwapBuffersInternal(const gfx::Rect& pixel_damage_rect);
+
+  // Returns true if the front of |pending_swaps_| has completed, or has timed
+  // out by |now|.
+  bool IsFirstPendingSwapReadyToDisplay(
+    const base::TimeTicks& now);
+  // Sets the CALayer contents to the IOSurface for the front of
+  // |pending_swaps_|, and removes it from the queue.
+  void DisplayFirstPendingSwapImmediately();
+  // Force that all of |pending_swaps_| displayed immediately, and the list be
+  // cleared.
+  void FinishAllPendingSwaps();
+  // Callback issued during the next vsync period ofter a SwapBuffers call,
+  // to check if the swap is completed, and display the frame. Note that if
+  // another SwapBuffers happens before this callback, the pending swap will
+  // be tested at that time, too.
+  void CheckPendingSwapsCallback();
+  // Function to post the above callback. The argument |now| is passed as an
+  // argument to avoid redundant calls to base::TimeTicks::Now.
+  void PostCheckPendingSwapsCallbackIfNeeded(const base::TimeTicks& now);
+
   scoped_ptr<ImageTransportHelper> helper_;
   base::scoped_nsobject<CAContext> ca_context_;
   base::scoped_nsobject<CALayer> layer_;
 
-  // A phony NSView handle used to identify this.
-  gfx::AcceleratedWidget widget_;
-
   gfx::Size pixel_size_;
   float scale_factor_;
   std::vector<ui::LatencyInfo> latency_info_;
@@ -63,6 +88,19 @@ class ImageTransportSurfaceOverlayMac : public gfx::GLSurface,
   // consumed and reset when SwapBuffers is called. For now, only one overlay
   // plane is supported.
   gfx::GLImage* pending_overlay_image_;
+
+  // A queue of all frames that have been created by SwapBuffersInternal but
+  // have not yet been displayed. This queue is checked at the beginning of
+  // every swap and also by a callback.
+  std::deque<linked_ptr<PendingSwap>> pending_swaps_;
+
+  // The display link used to compute the time for callbacks.
+  scoped_refptr<ui::DisplayLinkMac> display_link_mac_;
+
+  // True if there is a pending call to CheckPendingSwapsCallback posted.
+  bool has_pending_callback_;
+
+  base::WeakPtrFactory<ImageTransportSurfaceOverlayMac> weak_factory_;
 };
 
 }  // namespace content