Mark copied textures as cleared when using GL_CHROMIUM_copy_texture.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
===================================================================
--- gpu/command_buffer/service/gles2_cmd_decoder.cc	(revision 136908)
+++ gpu/command_buffer/service/gles2_cmd_decoder.cc	(working copy)
@@ -8498,6 +8498,8 @@
     texture_manager()->SetLevelInfo(
         dest_info, GL_TEXTURE_2D, level, internal_format, source_width,
         source_height, 1, 0, internal_format, dest_type, true);
+  } else {
+    texture_manager()->SetLevelCleared(dest_info, GL_TEXTURE_2D, level);
   }
 
   state_dirty_ = true;