gpu: Add CHROMIUM_copy_image extension.

cc/test/test_web_graphics_context_3d.h

Index: cc/test/test_web_graphics_context_3d.h
diff --git a/cc/test/test_web_graphics_context_3d.h b/cc/test/test_web_graphics_context_3d.h
index 4f627a19ffa63ad2d42caa96c0a83052804ee07d..eff582504763f4035be77ea11d05deb3b6b59406 100644
--- a/cc/test/test_web_graphics_context_3d.h
+++ b/cc/test/test_web_graphics_context_3d.h
@@ -80,6 +80,16 @@ class TestWebGraphicsContext3D {
                                           const void* pixels) {}
   virtual void waitAsyncTexImage2DCHROMIUM(GLenum target) {}
   virtual void releaseTexImage2DCHROMIUM(GLenum target, GLint image_id) {}
+  virtual void copyImageSubDataCHROMIUM(GLint source_image_id,
+                                        GLint dest_texture_id,
+                                        GLint xoffset,
+                                        GLint yoffset,
+                                        GLint x,
+                                        GLint y,
+                                        GLsizei width,
+                                        GLsizei height,
+                                        GLint in_fence_id,
+                                        GLint out_fence_id) {}
   virtual void framebufferRenderbuffer(GLenum target,
                                        GLenum attachment,
                                        GLenum renderbuffertarget,