Ozone: Avoid blocking in Swapbuffer Call.

ui/gl/gl_surface.h

Index: ui/gl/gl_surface.h
diff --git a/ui/gl/gl_surface.h b/ui/gl/gl_surface.h
index 1302cce4e5331b558a502e4311fac3a1ed7e529a..7905a84ec55c22237fcf69f4477bc6cef6e7a514 100644
--- a/ui/gl/gl_surface.h
+++ b/ui/gl/gl_surface.h
@@ -7,6 +7,7 @@
 
 #include <string>
 
+#include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "build/build_config.h"
 #include "ui/gfx/native_widget_types.h"
@@ -72,9 +73,26 @@ class GL_EXPORT GLSurface : public base::RefCounted<GLSurface> {
   // FBO. Otherwise returns 0.
   virtual unsigned int GetBackingFrameBufferObject();
 
+  typedef base::Callback<void()> SwapCompletionCallback;
+  // Swaps front and back buffers. This has no effect for off-screen
+  // contexts. On some platforms, we want to send SwapBufferAck only after the
+  // surface is displayed on screen. The callback can be used to delay sending
+  // SwapBufferAck till that data is available.
+  virtual bool SwapBuffersAsync(const SwapCompletionCallback& callback);
+
   // Copy part of the backbuffer to the frontbuffer.
   virtual bool PostSubBuffer(int x, int y, int width, int height);
 
+  // Copy part of the backbuffer to the frontbuffer. On some platforms, we want
+  // to send SwapBufferAck only after the surface is displayed on screen. The
+  // callback can be used to delay sending SwapBufferAck till that data is
+  // available.
+  virtual bool PostSubBufferAsync(int x,
+                                  int y,
+                                  int width,
+                                  int height,
+                                  const SwapCompletionCallback& callback);
+
   // Initialize GL bindings.
   static bool InitializeOneOff();
 
@@ -169,7 +187,13 @@ class GL_EXPORT GLSurfaceAdapter : public GLSurface {
   bool DeferDraws() override;
   bool IsOffscreen() override;
   bool SwapBuffers() override;
+  bool SwapBuffersAsync(const SwapCompletionCallback& callback) override;
   bool PostSubBuffer(int x, int y, int width, int height) override;
+  bool PostSubBufferAsync(int x,
+                          int y,
+                          int width,
+                          int height,
+                          const SwapCompletionCallback& callback) override;
   bool SupportsPostSubBuffer() override;
   gfx::Size GetSize() override;
   void* GetHandle() override;