Re-land^2 WebVR compositor bypass via BrowserMain context + mailbox

chrome/browser/android/vr_shell/vr_shell.h

Index: chrome/browser/android/vr_shell/vr_shell.h
diff --git a/chrome/browser/android/vr_shell/vr_shell.h b/chrome/browser/android/vr_shell/vr_shell.h
index b887d507962ac933825e72fdb61c8cbb94f1a8e3..7c4730a719b5250cc0d12f3303b1477c4bdb712b 100644
--- a/chrome/browser/android/vr_shell/vr_shell.h
+++ b/chrome/browser/android/vr_shell/vr_shell.h
@@ -169,6 +169,8 @@ class VrShell : public device::GvrDelegate, content::WebContentsObserver {
       gvr::GvrApi* gvr_api,
       gvr::Sizei compositor_size,
       uint32_t device_id);
+  void OnSubmitWebVRFrameTransferred(int frame_index);
+  void OnSubmitWebVRFrameRendered(int frame_index);
 
  private:
   ~VrShell() override;
@@ -184,7 +186,9 @@ class VrShell : public device::GvrDelegate, content::WebContentsObserver {
 
   // device::GvrDelegate implementation
   void SetWebVRSecureOrigin(bool secure_origin) override;
-  void SubmitWebVRFrame() override;
+  void SubmitWebVRFrame(
+      int frame_index, const gpu::Mailbox& mailbox,
+      device::mojom::VRSubmitFrameClientPtr submit_client) override;
   void UpdateWebVRTextureBounds(int16_t frame_index,
                                 const gvr::Rectf& left_bounds,
                                 const gvr::Rectf& right_bounds) override;
@@ -205,6 +209,10 @@ class VrShell : public device::GvrDelegate, content::WebContentsObserver {
   std::unique_ptr<UiInterface> html_interface_;
   bool content_paused_ = false;
   bool webvr_mode_ = false;
+  int webvr_surface_handle_;
+  int webvr_frames_in_surface_queue_ = 0;
+  device::mojom::VRSubmitFrameClientPtr webvr_submit_client_transferring_;
+  device::mojom::VRSubmitFrameClientPtr webvr_submit_client_rendering_;
 
   content::WebContents* main_contents_ = nullptr;
   base::android::ScopedJavaGlobalRef<jobject> j_motion_event_synthesizer_;