gpu: Add CHROMIUM_copy_image extension.

ui/gl/gl_image_glx.cc

Index: ui/gl/gl_image_glx.cc
diff --git a/ui/gl/gl_image_glx.cc b/ui/gl/gl_image_glx.cc
index dae98231c50d071307fadd1f2f46bb52c844c1cd..85defa736525b85bba0d47556191e30aeeda09e7 100644
--- a/ui/gl/gl_image_glx.cc
+++ b/ui/gl/gl_image_glx.cc
@@ -194,6 +194,14 @@ bool GLImageGLX::CopyTexSubImage(unsigned target,
   return false;
 }
 
+bool GLImageGLX::CopySubImageData(unsigned texture_id,
+                                  const gfx::Point& offset,
+                                  const gfx::Rect& rect,
+                                  GLFence* in_fence,
+                                  GLFence* out_fence) {
+  return false;
+}
+
 bool GLImageGLX::ScheduleOverlayPlane(gfx::AcceleratedWidget widget,
                                       int z_order,
                                       gfx::OverlayTransform transform,