Cache pointers to histograms for recording event times.

ui/events/event.cc

Index: ui/events/event.cc
diff --git a/ui/events/event.cc b/ui/events/event.cc
index ca6704b6f8fa5b6e49888074b799c620b7bc90e2..b29c68daa83397fa9ffd6a4349c192f9d1f44c46 100644
--- a/ui/events/event.cc
+++ b/ui/events/event.cc
@@ -312,16 +312,17 @@ Event::Event(const base::NativeEvent& native_event,
       static_cast<base::HistogramBase::Sample>(delta.InMicroseconds());
   UMA_HISTOGRAM_CUSTOM_COUNTS("Event.Latency.Browser", delta_sample, 1, 1000000,
                               100);
-  std::string name_for_event =
-      base::StringPrintf("Event.Latency.Browser.%s", name_.c_str());
-  base::HistogramBase* counter_for_type =
+
+  // Though it seems inefficient to generate the string twice, the first
+  // instance will be used only for DCHECK builds and the second won't be
+  // executed at all if the histogram was previously accessed here.
+  STATIC_HISTOGRAM_POINTER_GROUP(
+      base::StringPrintf("Event.Latency.Browser.%s", name_.c_str()),
+      type_, ET_LAST, Add(delta_sample),
       base::Histogram::FactoryGet(
-          name_for_event,
-          1,
-          1000000,
-          100,
-          base::HistogramBase::kUmaTargetedHistogramFlag);
-  counter_for_type->Add(delta_sample);
+          base::StringPrintf("Event.Latency.Browser.%s", name_.c_str()),
+          1, 1000000, 100,
+          base::HistogramBase::kUmaTargetedHistogramFlag));
 
 #if defined(USE_X11)
   if (native_event->type == GenericEvent) {