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

chrome/browser/android/vr_shell/vr_shell_gl.h

Index: chrome/browser/android/vr_shell/vr_shell_gl.h
diff --git a/chrome/browser/android/vr_shell/vr_shell_gl.h b/chrome/browser/android/vr_shell/vr_shell_gl.h
index 24ce9627f29d5f2323d00e060f8e370615c26838..e38f8611892a2e53390203f92c8ea68f327dff6c 100644
--- a/chrome/browser/android/vr_shell/vr_shell_gl.h
+++ b/chrome/browser/android/vr_shell/vr_shell_gl.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_GL_H_
 
 #include <memory>
+#include <queue>
 
 #include "base/cancelable_callback.h"
 #include "base/macros.h"
@@ -79,7 +80,8 @@ class VrShellGl : public device::mojom::VRVSyncProvider {
   void UIPhysicalBoundsChanged(int width, int height);
   base::WeakPtr<VrShellGl> GetWeakPtr();
 
-  void UpdateWebVRTextureBounds(const gvr::Rectf& left_bounds,
+  void UpdateWebVRTextureBounds(int16_t frame_index,
+                                const gvr::Rectf& left_bounds,
                                 const gvr::Rectf& right_bounds);
   gvr::GvrApi* gvr_api();
   void SetGvrPoseForWebVr(const gvr::Mat4f& pose, uint32_t pose_num);
@@ -113,7 +115,7 @@ class VrShellGl : public device::mojom::VRVSyncProvider {
 
   void OnUIFrameAvailable();
   void OnContentFrameAvailable();
-  bool GetPixelEncodedPoseIndexByte(int* pose_index);
+  bool GetPixelEncodedFrameIndex(int* frame_index);
 
   void OnVSync();
 
@@ -122,7 +124,7 @@ class VrShellGl : public device::mojom::VRVSyncProvider {
 
   void ForceExitVr();
 
-  device::mojom::VRPosePtr GetPose();
+  void SendVSync(const base::TimeDelta& time, GetVSyncCallback callback);

[dcheng, 2017/01/18 23:58:07]

Ditto: pass TimeDelta by value

[mthiesse, 2017/01/19 01:19:08]

Done.

 
   // samplerExternalOES texture data for UI content image.
   int ui_texture_id_ = 0;
@@ -147,6 +149,8 @@ class VrShellGl : public device::mojom::VRVSyncProvider {
   std::unique_ptr<gvr::BufferViewport> webvr_left_viewport_;
   std::unique_ptr<gvr::BufferViewport> webvr_right_viewport_;
   std::unique_ptr<gvr::SwapChain> swap_chain_;
+  typedef std::pair<gvr::Rectf, gvr::Rectf> BoundsPair;
+  std::queue<std::pair<uint8_t, BoundsPair>> pending_bounds_;
 
   // Current sizes for the render buffers.
   gvr::Sizei render_size_primary_;
@@ -167,10 +171,6 @@ class VrShellGl : public device::mojom::VRVSyncProvider {
   gvr::Sizei content_tex_physical_size_ = {0, 0};
   gvr::Sizei ui_tex_physical_size_ = {0, 0};
 
-  // The pose ring buffer size must be a power of two to avoid glitches when
-  // the pose index wraps around. It should be large enough to handle the
-  // current backlog of poses which is 2-3 frames.
-  static constexpr int kPoseRingBufferSize = 8;
   std::vector<gvr::Mat4f> webvr_head_pose_;
   int webvr_texture_id_ = 0;
   bool web_vr_mode_;
@@ -196,8 +196,8 @@ class VrShellGl : public device::mojom::VRVSyncProvider {
   base::WeakPtr<VrShellDelegate> delegate_provider_;
   scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner_;
 
-  uint32_t pose_index_ = 1;
-  int last_pose_ = 0;
+  uint8_t frame_index_ = 0;
+  int16_t last_frame_index_ = 0;

[dcheng, 2017/01/18 23:58:07]

Some comments here would be helpful. I'm not an expert in this code, so I don't
quite understand why one is uint8_t, while another field which is similarly
named is int16_t. It could just be a naming issue as well?

[mthiesse, 2017/01/19 01:19:08]

I did this so it could be initialized to -1... and then didn't initialize it to
-1.

In practice it doesn't really matter, but to be correct it shouldn't be
initialized to an in-band value of frame_index_.

Added a comment.

 
   base::WeakPtrFactory<VrShellGl> weak_ptr_factory_;