gpu: Add CHROMIUM_copy_image extension.

ui/gl/gl_image.h

Index: ui/gl/gl_image.h
diff --git a/ui/gl/gl_image.h b/ui/gl/gl_image.h
index 8f3ef54be21cd415edde3dd8784e944f371aa73a..90eaad96a2872649c0038ee37d030390a3dfb986 100644
--- a/ui/gl/gl_image.h
+++ b/ui/gl/gl_image.h
@@ -62,6 +62,16 @@ class GL_EXPORT GLImage : public base::RefCounted<GLImage> {
                                const gfx::Point& offset,
                                const gfx::Rect& rect) = 0;
 
+  // Copy |rect| of image to |offset| in texture with |texture_id|.
+  // Returns true on success. Unlike above functions, this doesn't require
+  // the destination texture to be bound to a target and fences provide more
+  // efficient synchronization.
+  virtual bool CopySubImageData(unsigned texture_id,
+                                const gfx::Point& offset,
+                                const gfx::Rect& rect,
+                                GLFence* in_fence,
+                                GLFence* out_fence) = 0;
+
   // Schedule image as an overlay plane to be shown at swap time for |widget|.
   virtual bool ScheduleOverlayPlane(gfx::AcceleratedWidget widget,
                                     int z_order,