Add further VR metrics.

This add media watch time in VR, session time, navigations,
and RAPPOR.

BUG=641472, 656105

Review-Url: https://codereview.chromium.org/2494503002
Cr-Commit-Position: refs/heads/master@{#432732}
diff --git a/content/public/browser/web_contents.h b/content/public/browser/web_contents.h
index 34befb7..197afd3f 100644
--- a/content/public/browser/web_contents.h
+++ b/content/public/browser/web_contents.h
@@ -731,6 +731,9 @@
   // Sets whether the WebContents is for overlaying content on a page.
   virtual void SetIsOverlayContent(bool is_overlay_content) = 0;
 
+  virtual int GetCurrentlyPlayingVideoCount() = 0;
+  virtual bool IsFullscreen() = 0;
+
 #if defined(OS_ANDROID)
   CONTENT_EXPORT static WebContents* FromJavaWebContents(
       const base::android::JavaRef<jobject>& jweb_contents_android);