gpu: Add CHROMIUM_copy_image extension.

ui/gl/gl_image_stub.cc

Index: ui/gl/gl_image_stub.cc
diff --git a/ui/gl/gl_image_stub.cc b/ui/gl/gl_image_stub.cc
index d8fe474c28345991e7f5b623143b37adbf182c2d..a23b32e3b1abaf5da95173a28954a29434d2b313 100644
--- a/ui/gl/gl_image_stub.cc
+++ b/ui/gl/gl_image_stub.cc
@@ -32,6 +32,14 @@ bool GLImageStub::CopyTexSubImage(unsigned target,
   return true;
 }
 
+bool GLImageStub::CopySubImageData(unsigned texture_id,
+                                   const gfx::Point& offset,
+                                   const gfx::Rect& rect,
+                                   GLFence* in_fence,
+                                   GLFence* out_fence) {
+  return false;
+}
+
 bool GLImageStub::ScheduleOverlayPlane(gfx::AcceleratedWidget widget,
                                        int z_order,
                                        gfx::OverlayTransform transform,