Ensure that the web contents trying to access native VR Shell is the webcontents we created.

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 c834ed043772a3c444e3819282f49d400f558cf1..a9ea9076f2907e1428ffc95be4b7276a5743c27b 100644
--- a/chrome/browser/android/vr_shell/vr_shell.h
+++ b/chrome/browser/android/vr_shell/vr_shell.h
@@ -21,6 +21,7 @@
 
 namespace content {
 class ContentViewCore;
+class WebContents;
 }
 
 namespace ui {
@@ -62,7 +63,8 @@ class VrShell : public device::GvrDelegate {
                     bool enabled);
 
   // html/js UI hooks.
-  static base::WeakPtr<VrShell> GetWeakPtr();
+  static base::WeakPtr<VrShell> GetWeakPtr(
+      const content::WebContents* web_contents);
   UiScene* GetScene();
   void OnDomContentsLoaded();
   void SetUiTextureSize(int width, int height);