Refactor GvrDelegate ownership into GvrDelegateProvider and fix more threading violations.

chrome/browser/android/vr_shell/vr_compositor.h

Index: chrome/browser/android/vr_shell/vr_compositor.h
diff --git a/chrome/browser/android/vr_shell/vr_compositor.h b/chrome/browser/android/vr_shell/vr_compositor.h
index a0e872029c7484871c01c28b90763d5adba8e413..533367bde06615f1f51139a47da9b3d1d639528c 100644
--- a/chrome/browser/android/vr_shell/vr_compositor.h
+++ b/chrome/browser/android/vr_shell/vr_compositor.h
@@ -36,7 +36,6 @@ class VrCompositor : public content::CompositorClient {
 
   void SurfaceDestroyed();
   void SetWindowBounds(gfx::Size size);
-  gfx::Size GetWindowBounds() { return bounds_; }
   void SurfaceChanged(jobject surface);
   void SetLayer(content::WebContents* web_contents);
 
@@ -46,7 +45,6 @@ class VrCompositor : public content::CompositorClient {
 
  private:
   std::unique_ptr<content::Compositor> compositor_;
-  gfx::Size bounds_;
 
   cc::Layer* layer_ = nullptr;
   cc::Layer* layer_parent_ = nullptr;