Allow VRDisplay to specify which frame the layer bounds should be updated at.

chrome/browser/android/vr_shell/vr_shell_gl.cc

 // Copyright 2016 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 "chrome/browser/android/vr_shell/vr_shell_gl.h"
 
 #include "base/android/jni_android.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 916 matching lines @@
   if (ready_to_draw_) {
     draw_task_.Reset(base::Bind(&VrShellGl::DrawFrame, base::Unretained(this)));
     ScheduleNextDrawFrame();
   }
 }
 
 void VrShellGl::SetWebVrMode(bool enabled) {
   web_vr_mode_ = enabled;
 }
 
-void VrShellGl::UpdateWebVRTextureBounds(const gvr::Rectf& left_bounds,
+void VrShellGl::UpdateWebVRTextureBounds(uint32_t frame_index,
+                                         const gvr::Rectf& left_bounds,
                                          const gvr::Rectf& right_bounds) {
+  // TODO(klausw): Only update the texture bounds once we're rendering frame
+  // |for_frame_index|.

[dcheng, 2017/01/10 06:53:19]

Sorry for missing this in my review queue. Is there any way to upstream the IPC
changes with the complete implementation changes?

   webvr_left_viewport_->SetSourceUv(left_bounds);
   webvr_right_viewport_->SetSourceUv(right_bounds);
 }
 
 gvr::GvrApi* VrShellGl::gvr_api() {
   return gvr_api_.get();
 }
 
 void VrShellGl::ContentBoundsChanged(int width, int height) {
   TRACE_EVENT0("gpu", "VrShellGl::ContentBoundsChanged");
@@ skipping 48 matching lines @@
 void VrShellGl::ForceExitVr() {
   main_thread_task_runner_->PostTask(
       FROM_HERE, base::Bind(&VrShell::ForceExitVr, weak_vr_shell_));
 }
 
 void VrShellGl::UpdateScene(std::unique_ptr<base::ListValue> commands) {
   scene_->HandleCommands(std::move(commands), TimeInMicroseconds());
 }
 
 }  // namespace vr_shell