Pause drawing webvr when the App button is pressed

chrome/browser/android/vr_shell/vr_gl_thread.h

Index: chrome/browser/android/vr_shell/vr_gl_thread.h
diff --git a/chrome/browser/android/vr_shell/vr_gl_thread.h b/chrome/browser/android/vr_shell/vr_gl_thread.h
index 9e35938f3b427a7c9aa092ddaf9468bc8c226b84..4bedaa380835a44e13c3f6933a25fc93183499c6 100644
--- a/chrome/browser/android/vr_shell/vr_gl_thread.h
+++ b/chrome/browser/android/vr_shell/vr_gl_thread.h
@@ -11,6 +11,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread.h"
+#include "chrome/browser/android/vr_shell/vr_thread_envoy.h"
 #include "third_party/gvr-android-sdk/src/libraries/headers/vr/gvr/capi/include/gvr_types.h"
 
 namespace vr_shell {
@@ -20,7 +21,7 @@ class UiSceneManager;
 class VrShell;
 class VrShellGl;
 
-class VrGLThread : public base::Thread {
+class VrGLThread : public VrThreadEnvoy, public base::Thread {
  public:
   VrGLThread(
       const base::WeakPtr<VrShell>& weak_vr_shell,
@@ -30,11 +31,17 @@ class VrGLThread : public base::Thread {
       bool reprojected_rendering);
 
   ~VrGLThread() override;
+  void PostToMainThread(const base::Closure& task);
   base::WeakPtr<VrShellGl> GetVrShellGl() { return weak_vr_shell_gl_; }
   base::WeakPtr<UiSceneManager> GetSceneManager() {
     return weak_scene_manager_;
   }
 
+  // VrThreadEnvoy implementation.
+  base::WeakPtr<VrShell> GetVrShell() override;
+  scoped_refptr<base::SingleThreadTaskRunner> GetMainThreadTaskRunner()
+      override;
+
  protected:
   void Init() override;
   void CleanUp() override;
@@ -54,6 +61,8 @@ class VrGLThread : public base::Thread {
   bool initially_web_vr_;
   bool reprojected_rendering_;
 
+  base::WeakPtrFactory<VrGLThread> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(VrGLThread);
 };