Add Perceived PageLoad Time (PPLT) metrics for Prerender Experiments,...

chrome/browser/tab_contents/tab_contents.cc

Index: chrome/browser/tab_contents/tab_contents.cc
===================================================================
--- chrome/browser/tab_contents/tab_contents.cc	(revision 72357)
+++ chrome/browser/tab_contents/tab_contents.cc	(working copy)
@@ -375,6 +375,7 @@
       waiting_for_response_(false),
       max_page_id_(-1),
       current_load_start_(),
+      pplt_load_start_(),
       load_state_(net::LOAD_STATE_IDLE),
       load_state_host_(),
       upload_size_(0),
@@ -1654,6 +1655,9 @@
       Source<NavigationController>(&controller_),
       Details<ProvisionalLoadDetails>(&details));
   if (is_main_frame) {
+    // Record the beginning of a new PPLT navigation.
+    pplt_load_start_ = base::TimeTicks::Now();
+
     // If we're displaying a network error page do not reset the content
     // settings delegate's cookies so the user has a chance to modify cookie
     // settings.
@@ -2814,6 +2818,24 @@
 
   SetIsLoading(false, details.get());
 
+  // Compute the PPLT metric and report it in a histogram, if needed.
+  PrerenderManager* pm = profile()->GetPrerenderManager();

[cbentzel, 2011/01/26 19:38:36]

Can you move this into PrerenderManager or PrerenderContents?

[tburkard, 2011/01/26 20:05:50]

Done.

+  if (pm != NULL && !pplt_load_start_.is_null() &&
+      (pm->mode() == PrerenderManager::kExperimentControlGroup ||
+       pm->mode() == PrerenderManager::kExperimentPrerenderGroup)) {
+    base::TimeDelta elapsed = base::TimeTicks::Now() - pplt_load_start_;
+    if (pm->mode() == PrerenderManager::kExperimentControlGroup) {
+      UMA_HISTOGRAM_TIMES("PLT.PerceivedPageLoadTime_PrerenderControl",
+                          elapsed);
+    } else {
+      UMA_HISTOGRAM_TIMES("PLT.PerceivedPageLoadTime_PrerenderTreatment",
+                          elapsed);
+    }
+  }
+
+  // Reset the PPLT metric.
+  pplt_load_start_ = base::TimeTicks();
+
   // Notify observers about navigation.
   FOR_EACH_OBSERVER(WebNavigationObserver, web_navigation_observers_,
                     DidStopLoading());
@@ -3393,12 +3415,8 @@
 bool TabContents::MaybeUsePreloadedPage(const GURL& url) {
   PrerenderManager* pm = profile()->GetPrerenderManager();
   if (pm != NULL) {
-    if (pm->MaybeUsePreloadedPage(this, url)) {
-      // TODO(tburkard): If the preloaded page has not finished preloading
-      // yet, we should not do this.
-      DidStopLoading();
+    if (pm->MaybeUsePreloadedPage(this, url))
       return true;
-    }
   }
   return false;
 }