Add histograms for prerender rel types.

chrome/browser/prerender/prerender_link_manager.cc

Index: chrome/browser/prerender/prerender_link_manager.cc
diff --git a/chrome/browser/prerender/prerender_link_manager.cc b/chrome/browser/prerender/prerender_link_manager.cc
index 787a8116836bade0505a3eb202a23a71907d22c8..8fae9e73c48bc6d776d7eb130ca1218ac1356e38 100644
--- a/chrome/browser/prerender/prerender_link_manager.cc
+++ b/chrome/browser/prerender/prerender_link_manager.cc
@@ -11,6 +11,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/field_trial.h"
+#include "base/metrics/histogram.h"
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/prerender/prerender_handle.h"
 #include "chrome/browser/prerender/prerender_manager.h"
@@ -41,7 +42,7 @@ bool ShouldStartRelNextPrerenders() {
   return experiment_name.find("Yes") != std::string::npos;
 }
 
-bool ShouldStartPrerender(uint32 rel_types) {
+bool ShouldStartPrerender(const uint32 rel_types) {
   const bool should_start_rel_next_prerenders =
       ShouldStartRelNextPrerenders();
 
@@ -54,6 +55,31 @@ bool ShouldStartPrerender(uint32 rel_types) {
   return false;
 }
 
+COMPILE_ASSERT(PrerenderRelTypePrerender == 0x1,
+               RelTypeHistogramEnum_must_match_PrerenderRelType);
+COMPILE_ASSERT(PrerenderRelTypeNext == 0x2,
+               RelTypeHistogramEnum_must_match_PrerenderRelType);
+enum RelTypeHistogramEnum {

[gavinp, 2013/12/20 19:56:43]

Our coding standard doesn't define an order for translation units, only for
classes. The restriction on ordering is within classes, see
http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Declar...
. 

So I moved the enum down here, closer to the histogram reporting functions, for
easier readability. What do you think?

+  RelTypeHistogramEnumNone = 0,
+  RelTypeHistogramEnumPrerender = PrerenderRelTypePrerender,
+  RelTypeHistogramEnumNext = PrerenderRelTypeNext,
+  RelTypeHistogramEnumPrerenderAndNext =
+      PrerenderRelTypePrerender | PrerenderRelTypeNext,
+  RelTypeHistogramEnumMax,
+};
+
+void RecordLinkManagerAdded(const uint32 rel_types) {
+  const uint32 enum_value = rel_types & (RelTypeHistogramEnumMax - 1);
+  UMA_HISTOGRAM_ENUMERATION("Prerender.RelTypesLinkAdded", enum_value,
+                            RelTypeHistogramEnumMax);
+}
+
+void RecordLinkManagerStarting(const uint32 rel_types) {
+  const uint32 enum_value = rel_types & (RelTypeHistogramEnumMax - 1);
+  UMA_HISTOGRAM_ENUMERATION("Prerender.RelTypesLinkStarted", enum_value,
+                            RelTypeHistogramEnumMax);
+}
+
 void Send(int child_id, IPC::Message* raw_message) {
   using content::RenderProcessHost;
   scoped_ptr<IPC::Message> own_message(raw_message);
@@ -105,6 +131,7 @@ void PrerenderLinkManager::OnAddPrerender(int launcher_child_id,
       prerender(launcher_child_id, prerender_id, url, rel_types, referrer, size,
                 render_view_route_id, manager_->GetCurrentTimeTicks());
   prerenders_.push_back(prerender);
+  RecordLinkManagerAdded(rel_types);
   StartPrerenders();
 }
 
@@ -293,6 +320,7 @@ void PrerenderLinkManager::StartPrerenders() {
     handle->SetObserver(this);
     if (handle->IsPrerendering())
       OnPrerenderStart(handle);
+    RecordLinkManagerStarting((*i)->rel_types);
 
     running_launcher_and_render_view_routes.insert(
         launcher_and_render_view_route);