[NoStatePrefetch] Add performance histograms.

chrome/browser/ui/browser_navigator.cc

Index: chrome/browser/ui/browser_navigator.cc
diff --git a/chrome/browser/ui/browser_navigator.cc b/chrome/browser/ui/browser_navigator.cc
index 816f1d774a0349ed9946ed8467e0660eb63c959b..3fa116bd243cfbd07f0ce7b5351a2201df058568 100644
--- a/chrome/browser/ui/browser_navigator.cc
+++ b/chrome/browser/ui/browser_navigator.cc
@@ -385,7 +385,7 @@ bool SwapInPrerender(const GURL& url, chrome::NavigateParams* params) {
     return true;
 
   prerender::PrerenderManager* prerender_manager =
-      prerender::PrerenderManagerFactory::GetForProfile(profile);
+      prerender::PrerenderManagerFactory::GetForBrowserContext(profile);

[mattcary, 2016/09/14 12:33:21]

Here and elsewhere, the profile is gotten from the BrowserContext, above, and it
seems like it would be cleaner to pass that in rather than the profile?

[droger, 2016/09/14 14:15:42]

Profile is the BrowserContext (by inheritance).
FromBrowserContext() is just a static cast, and the two objects are literally
the same.
This property is not just an implementation detail, as Chrome assumes this
everywhere.

So I think it's fine to conflate the two here in this specific file, since we
need to have the profile for other calls in any case (i.e. line 383).


For other files though, I double checked and you're right, there are a few cases
where the conversion from BrowserContext to Profile is now useless, that I
missed in my first pass. Fixed now.

   return prerender_manager &&
       prerender_manager->MaybeUsePrerenderedPage(url, params);
 }