Fix PPLT metric for the new TabContents based prerendering

R=cbentzel@chromium.org, dominich@chromium.org
Review URL: http://codereview.chromium.org/7066011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@86364 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/prerender/prerender_manager.cc

@@ -14,6 +14,7 @@
 #include "chrome/browser/favicon/favicon_tab_helper.h"
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/prerender/prerender_final_status.h"
+#include "chrome/browser/prerender/prerender_observer.h"
 #include "chrome/browser/prerender/prerender_tracker.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/tab_contents/tab_contents_wrapper.h"
@@ -608,6 +609,14 @@ bool PrerenderManager::MaybeUsePreloadedPage(TabContents* tab_contents,
         urls);
   }
 
+  // Update PPLT metrics:
+  // If the tab has finished loading, record a PPLT of 0.
+  // If the tab is still loading, reset its start time to the current time.
+  PrerenderObserver* prerender_observer =
+      new_tab_contents->prerender_observer();
+  DCHECK(prerender_observer != NULL);
+  prerender_observer->PrerenderSwappedIn();
+
   // See if we have any pending prerender requests for this routing id and start
   // the preload if we do.
   std::pair<int, int> child_route_pair = std::make_pair(child_id, route_id);

chrome/browser/prerender/prerender_observer.cc

@@ -44,10 +44,6 @@ void PrerenderObserver::OnDidStartProvisionalLoadForFrame(int64 frame_id,
                                                           bool is_main_frame,
                                                           bool has_opener_set,
                                                           const GURL& url) {
-  // Don't include prerendered pages in the PPLT metric until after they are
-  // swapped in.
-  if (IsPrerendering())
-    return;
   if (is_main_frame) {
     // Record the beginning of a new PPLT navigation.
     pplt_load_start_ = base::TimeTicks::Now();
@@ -57,11 +53,9 @@ void PrerenderObserver::OnDidStartProvisionalLoadForFrame(int64 frame_id,
 void PrerenderObserver::DidStopLoading() {
   // Don't include prerendered pages in the PPLT metric until after they are
   // swapped in.
-  if (IsPrerendering())
-    return;
 
   // Compute the PPLT metric and report it in a histogram, if needed.
-  if (!pplt_load_start_.is_null()) {
+  if (!pplt_load_start_.is_null() && !IsPrerendering()) {
     PrerenderManager::RecordPerceivedPageLoadTime(
         base::TimeTicks::Now() - pplt_load_start_, tab_contents());
   }
@@ -92,4 +86,17 @@ bool PrerenderObserver::IsPrerendering() {
   return prerender_manager->IsTabContentsPrerendering(tab_contents());
 }
 
+void PrerenderObserver::PrerenderSwappedIn() {
+  // Ensure we are not prerendering any more.
+  DCHECK(!IsPrerendering());
+  if (pplt_load_start_.is_null()) {
+    // If we have already finished loading, report a 0 PPLT.
+    PrerenderManager::RecordPerceivedPageLoadTime(base::TimeDelta(),
+                                                  tab_contents());
+  } else {
+    // If we have not finished loading yet, rebase the start time to now.
+    pplt_load_start_ = base::TimeTicks::Now();
+  }
+}
+
 }  // namespace prerender

chrome/browser/prerender/prerender_observer.h

@@ -36,6 +36,9 @@ class PrerenderObserver : public TabContentsObserver {
                                          bool has_opener_set,
                                          const GURL& url);
 
+  // Called when this prerendered TabContents has just been swapped in.
+  void PrerenderSwappedIn();
+
  private:
   // Retrieves the PrerenderManager, or NULL, if none was found.
   PrerenderManager* MaybeGetPrerenderManager();

chrome/browser/prerender/prerender_render_view_host_observer.cc

@@ -34,6 +34,17 @@ bool PrerenderRenderViewHostObserver::OnMessageReceived(
   IPC_BEGIN_MESSAGE_MAP(PrerenderRenderViewHostObserver, message)
     IPC_MESSAGE_HANDLER(ViewHostMsg_DidStartProvisionalLoadForFrame,
                         OnDidStartProvisionalLoadForFrame)
+    IPC_MESSAGE_UNHANDLED(handled = false)
+  IPC_END_MESSAGE_MAP()
+
+  // If this was a DidStartProvisionalLoadForFrame message, we don't want to
+  // to consume it, so return false;
+  if (handled)
+    return false;
+
+  // The following messages we do want to consume.
+  handled = true;
+  IPC_BEGIN_MESSAGE_MAP(PrerenderRenderViewHostObserver, message)
     IPC_MESSAGE_HANDLER(IconHostMsg_UpdateFaviconURL, OnUpdateFaviconURL)
     IPC_MESSAGE_HANDLER(ViewHostMsg_MaybeCancelPrerenderForHTML5Media,
                         OnMaybeCancelPrerenderForHTML5Media)

chrome/browser/ui/tab_contents/tab_contents_wrapper.h

@@ -166,6 +166,10 @@ class TabContentsWrapper : public TabContentsObserver,
     return translate_tab_helper_.get();
   }
 
+  prerender::PrerenderObserver* prerender_observer() {
+    return prerender_observer_.get();
+  }
+
   // Overrides -----------------------------------------------------------------
 
   // TabContentsObserver overrides: