Support caching histograms so that a lookup isn't done in each iteration.

third_party/WebKit/Source/core/layout/HitTestCache.cpp

Index: third_party/WebKit/Source/core/layout/HitTestCache.cpp
diff --git a/third_party/WebKit/Source/core/layout/HitTestCache.cpp b/third_party/WebKit/Source/core/layout/HitTestCache.cpp
index c38df2b8c877b73fe215a4352b2c8c342c80d133..2039732706188aae194aa1cc0cb34f8cc4bbc030 100644
--- a/third_party/WebKit/Source/core/layout/HitTestCache.cpp
+++ b/third_party/WebKit/Source/core/layout/HitTestCache.cpp
@@ -4,6 +4,7 @@
 
 #include "core/layout/HitTestCache.h"
 
+#include "platform/Histogram.h"
 #include "public/platform/Platform.h"
 
 namespace blink {
@@ -28,7 +29,8 @@ bool HitTestCache::lookupCachedResult(HitTestResult& hitResult, uint64_t domTree
             }
         }
     }
-    Platform::current()->histogramEnumeration("Event.HitTest", static_cast<int>(metric), static_cast<int>(HitHistogramMetric::MAX_HIT_METRIC));
+    DEFINE_STATIC_LOCAL(EnumerationHistogram, hitTestHistogram, ("Event.HitTest", static_cast<int32_t>(HitHistogramMetric::MAX_HIT_METRIC)));
+    hitTestHistogram.count(static_cast<int32_t>(metric));
     return result;
 }