VR: Make sure GL thread is started before binding callbacks to it.

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 1837b884cc58f59d80331f350fc4c987a9925632..31db7e8230297d8efc31d9b0d5ea6db9e3659b9d 100644
--- a/chrome/browser/android/vr_shell/vr_shell.h
+++ b/chrome/browser/android/vr_shell/vr_shell.h
@@ -166,7 +166,8 @@ class VrShell : public device::PresentingGvrDelegate,
 
  private:
   ~VrShell() override;
-  void PostToGlThreadWhenReady(const base::Closure& task);
+  void WaitForGlThread();
+  void PostToGlThread(const base::Closure& task);
   void SetUiState();
 
   // device::GvrDelegate implementation.
@@ -214,6 +215,7 @@ class VrShell : public device::PresentingGvrDelegate,
 
   scoped_refptr<base::SingleThreadTaskRunner> main_thread_task_runner_;
   std::unique_ptr<VrGLThread> gl_thread_;
+  bool thread_started_ = false;
   UiInterface* ui_;
   bool reprojected_rendering_;