Prerender: Remove PerceivedPLT histograms

chrome/browser/prerender/prerender_tab_helper.h

Index: chrome/browser/prerender/prerender_tab_helper.h
diff --git a/chrome/browser/prerender/prerender_tab_helper.h b/chrome/browser/prerender/prerender_tab_helper.h
index f944aa10b13abcaa113d173514ab49ed52dafaf6..49e136b35851044844a933c5a732ca6b524a37df 100644
--- a/chrome/browser/prerender/prerender_tab_helper.h
+++ b/chrome/browser/prerender/prerender_tab_helper.h
@@ -31,7 +31,6 @@ class PrerenderTabHelper
   // content::WebContentsObserver implementation.
   void DidGetRedirectForResourceRequest(
       const content::ResourceRedirectDetails& details) override;
-  void DidStopLoading() override;
   void DidStartNavigation(
       content::NavigationHandle* navigation_handle) override;
   void DidFinishNavigation(
@@ -52,10 +51,6 @@ class PrerenderTabHelper
   explicit PrerenderTabHelper(content::WebContents* web_contents);
   friend class content::WebContentsUserData<PrerenderTabHelper>;
 
-  void RecordPerceivedPageLoadTime(
-      base::TimeDelta perceived_page_load_time,
-      double fraction_plt_elapsed_at_swap_in);
-
   // Retrieves the PrerenderManager, or NULL, if none was found.
   PrerenderManager* MaybeGetPrerenderManager() const;
 
@@ -76,18 +71,7 @@ class PrerenderTabHelper
   // relevant prerender. Otherwise, ORIGIN_NONE.
   Origin origin_;
 
-  // System time at which the current load was started for the purpose of
-  // the perceived page load time (PPLT). If null, there is no current
-  // load.
-  base::TimeTicks pplt_load_start_;
-
-  // System time at which the actual pageload started (pre-swapin), if
-  // a applicable (in cases when a prerender that was still loading was
-  // swapped in).
-  base::TimeTicks actual_load_start_;
-
-  // Record the most recent swap time. This differs from |pplt_load_start_| in
-  // that it is not reset in various circumstances, like a load being stopped.
+  // Record the most recent swap time.
   base::TimeTicks swap_ticks_;
 
   // Current URL being loaded.