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

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

Index: third_party/WebKit/Source/core/layout/LayoutView.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutView.cpp b/third_party/WebKit/Source/core/layout/LayoutView.cpp
index 5ea72b0b474149b6d37b466e1e69c05fd7e99fd4..d74ca5daaf6a50ba4115e63f0e406a9cb4eae20d 100644
--- a/third_party/WebKit/Source/core/layout/LayoutView.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutView.cpp
@@ -66,7 +66,13 @@ public:
     ~HitTestLatencyRecorder()
     {
         int duration = static_cast<int>((WTF::monotonicallyIncreasingTime() - m_start) * 1000000);
-        Platform::current()->histogramCustomCounts(m_allowsChildFrameContent ? "Event.Latency.HitTestRecursive" : "Event.Latency.HitTest", duration, 0, 10000000, 100);
+        if (m_allowsChildFrameContent) {
+            static Platform::HistogramCacheSlot histogramCache = 0;
+            Platform::current()->histogramCustomCounts("Event.Latency.HitTestRecursive", duration, 0, 10000000, 100, &histogramCache);

[esprehn, 2016/01/29 23:05:40]

DEFINE_STATIC_LOCAL(Histogram, hitTestLatency,
("Event.Latency.HitTestRecursive", 0, 10000000, 100));

hitTestLatency.record(duration);

+        } else {
+            static Platform::HistogramCacheSlot histogramCache = 0;
+            Platform::current()->histogramCustomCounts("Event.Latency.HitTest", duration, 0, 10000000, 100, &histogramCache);
+        }
     }
 
 private: