Clean up some VrShell threading issues and remove unnecessary WeakPtr types.

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 5de0c3948a78086d3c7a81a4d99de9a96538c95a..4b4ea45fae0346ec061c93112318180ed6beb889 100644
--- a/chrome/browser/android/vr_shell/vr_shell.h
+++ b/chrome/browser/android/vr_shell/vr_shell.h
@@ -108,6 +108,7 @@ class VrShell : public device::GvrDelegate, content::WebContentsObserver {
 
   void SurfacesChanged(jobject content_surface, jobject ui_surface);
   void GvrDelegateReady();
+  void AppButtonPressed();
 
   void ContentBoundsChanged(
       JNIEnv* env,
@@ -136,6 +137,7 @@ class VrShell : public device::GvrDelegate, content::WebContentsObserver {
  private:
   ~VrShell() override;
   void SetShowingOverscrollGlow(bool showing_glow);
+  void PostToGlThreadWhenReady(const base::Closure& task);
 
   // content::WebContentsObserver implementation. All called on UI thread.
   void RenderViewHostChanged(content::RenderViewHost* old_host,