Encode frame number in pixel data for pose sync

chrome/browser/android/vr_shell/vr_shell.h

 // 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.
 
 #ifndef CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_H_
 #define CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_H_
 
 #include <jni.h>
 #include <memory>
 #include <vector>
@@ skipping 60 matching lines @@
       const content::WebContents* web_contents);
   UiScene* GetScene();
   void OnDomContentsLoaded();
 
   // device::GvrDelegate implementation
   void SetWebVRSecureOrigin(bool secure_origin) override;
   void SubmitWebVRFrame() override;
   void UpdateWebVRTextureBounds(
       int eye, float left, float top, float width, float height) override;
   gvr::GvrApi* gvr_api() override;
+  void SetGvrPoseForWebVr(const gvr::Mat4f& pose, uint32_t pose_num) override;
 
   void ContentSurfaceChanged(
       JNIEnv* env,
       const base::android::JavaParamRef<jobject>& object,
       jint width,
       jint height,
       const base::android::JavaParamRef<jobject>& surface);
   void UiSurfaceChanged(
       JNIEnv* env,
       const base::android::JavaParamRef<jobject>& object,
@@ skipping 63 matching lines @@
 
   gvr::Vec3f target_point_;
   const ContentRectangle* target_element_ = nullptr;
   VrInputManager* current_input_target_ = nullptr;
   int ui_tex_width_ = 0;
   int ui_tex_height_ = 0;
 
   bool webvr_mode_ = false;
   bool webvr_secure_origin_ = false;
   int64_t webvr_warning_end_nanos_ = 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_;
 
   std::unique_ptr<VrController> controller_;
   scoped_refptr<VrInputManager> content_input_manager_;
   scoped_refptr<VrInputManager> ui_input_manager_;
 
   base::WeakPtrFactory<VrShell> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(VrShell);
 };
 
 bool RegisterVrShell(JNIEnv* env);
 
 }  // namespace vr_shell
 
 #endif  // CHROME_BROWSER_ANDROID_VR_SHELL_VR_SHELL_H_