exo: Fix use of invalid texture mailbox.

components/exo/buffer.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 "components/exo/buffer.h"
 
 #include <GLES2/gl2.h>
 #include <GLES2/gl2ext.h>
 #include <GLES2/gl2extchromium.h>
 #include <stdint.h>
@@ skipping 446 matching lines @@
     contents_texture_ = base::MakeUnique<Texture>(
         context_factory, context_provider.get(), gpu_memory_buffer_.get(),
         texture_target_, query_type_);
   }
 
   if (use_zero_copy_) {
     // Zero-copy means using the contents texture directly.
     Texture* texture = contents_texture_.get();
 
     // This binds the latest contents of this buffer to |texture|.
-    resource->mailbox_holder = gpu::MailboxHolder(
-        texture->mailbox(), texture->BindTexImage(), texture_target_);
+    gpu::SyncToken sync_token = texture->BindTexImage();
 
+    resource->mailbox_holder =
+        gpu::MailboxHolder(texture->mailbox(), sync_token, texture_target_);
     resource->is_overlay_candidate = is_overlay_candidate_;
 
     // The contents texture will be released when no longer used by the
     // compositor.
     compositor_frame_sink_holder_->SetResourceReleaseCallback(
         resource_id,
         base::Bind(&Buffer::Texture::ReleaseTexImage, base::Unretained(texture),
                    base::Bind(&Buffer::ReleaseContentsTexture, AsWeakPtr(),
                               base::Passed(&contents_texture_))));
     return true;
   }
 
   // Create a mailbox texture that we copy the buffer contents to.
   if (!texture_) {
     texture_ =
         base::MakeUnique<Texture>(context_factory, context_provider.get());
   }
 
   // Copy the contents of |contents_texture| to |texture| and produce a
   // texture mailbox from the result in |texture|.
   Texture* contents_texture = contents_texture_.get();
   Texture* texture = texture_.get();
 
   // The contents texture will be released when copy has completed.
   resource->mailbox_holder = gpu::MailboxHolder(
       texture->mailbox(),
       contents_texture->CopyTexImage(

[Alex Z., 2017/01/11 14:54:49]

Another sync token is created here. 
Does the texture also need to be bound before having the mailbox?

[reveman, 2017/01/11 18:06:53]

The mailbox for |texture| has already been created here as it's only GMB backed
textures that need to be bound before they have a mailbox. The mailbox for
|texture| is generated when creating the instance.

           texture, base::Bind(&Buffer::ReleaseContentsTexture, AsWeakPtr(),
                               base::Passed(&contents_texture_))),
       GL_TEXTURE_2D);
   resource->is_overlay_candidate = false;
 
   // The mailbox texture will be released when no longer used by the
   // compositor.
   compositor_frame_sink_holder_->SetResourceReleaseCallback(
       resource_id,
       base::Bind(&Buffer::Texture::Release, base::Unretained(texture),
@@ skipping 53 matching lines @@
   texture_ = std::move(texture);
 }
 
 void Buffer::ReleaseContentsTexture(std::unique_ptr<Texture> texture) {
   TRACE_EVENT0("exo", "Buffer::ReleaseContentsTexture");
   contents_texture_ = std::move(texture);
   Release();
 }
 
 }  // namespace exo