Fix screen mirroring on Chrome OS (ReflectorTexture partial swap)

content/browser/compositor/reflector_texture.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/compositor/reflector_texture.h"
 
 #include "components/display_compositor/gl_helper.h"
 #include "content/browser/compositor/owned_mailbox.h"
 #include "gpu/command_buffer/client/context_support.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
@@ skipping 13 matching lines @@
 
   texture_id_ = gl_helper_->ConsumeMailboxToTexture(mailbox_->mailbox(),
                                                     mailbox_->sync_token());
 }
 
 ReflectorTexture::~ReflectorTexture() {
   gl_helper_->DeleteTexture(texture_id_);
 }
 
 void ReflectorTexture::CopyTextureFullImage(const gfx::Size& size) {
+  is_texture_defined_ = true;
   gl_helper_->CopyTextureFullImage(texture_id_, size);
   // Insert a barrier to make the copy show up in the mirroring compositor's
   // mailbox. Since the the compositor contexts and the
   // ImageTransportFactory's
   // GLHelper are all on the same GPU channel, this is sufficient instead of
   // plumbing through a sync point.
   gl_helper_->InsertOrderingBarrier();
 }
 
 void ReflectorTexture::CopyTextureSubImage(const gfx::Rect& rect) {
+  DCHECK(is_texture_defined_);
   gl_helper_->CopyTextureSubImage(texture_id_, rect);
   // Insert a barrier for the same reason above.
   gl_helper_->InsertOrderingBarrier();
 }
 
 }  // namespace content