Allow safe per-thread heap compaction UMA reporting.

third_party/WebKit/Source/platform/heap/HeapCompact.cpp

Index: third_party/WebKit/Source/platform/heap/HeapCompact.cpp
diff --git a/third_party/WebKit/Source/platform/heap/HeapCompact.cpp b/third_party/WebKit/Source/platform/heap/HeapCompact.cpp
index 995a7d81ee7da83caecf3a89a4a87cc1c74d825c..9aee638ead8caf4a85f113db381f1a5d9820562b 100644
--- a/third_party/WebKit/Source/platform/heap/HeapCompact.cpp
+++ b/third_party/WebKit/Source/platform/heap/HeapCompact.cpp
@@ -428,14 +428,17 @@ void HeapCompact::finishThreadCompaction() {
   m_doCompact = false;
 
   double timeForHeapCompaction = WTF::currentTimeMS() - m_startCompactionTimeMS;
-  DEFINE_STATIC_LOCAL(CustomCountHistogram, timeForHeapCompactionHistogram,
-                      ("BlinkGC.TimeForHeapCompaction", 1, 10 * 1000, 50));
+  DEFINE_THREAD_SAFE_STATIC_LOCAL(
+      CustomCountHistogram, timeForHeapCompactionHistogram,
+      new CustomCountHistogram("BlinkGC.TimeForHeapCompaction", 1, 10 * 1000,
+                               50));
   timeForHeapCompactionHistogram.count(timeForHeapCompaction);
   m_startCompactionTimeMS = 0;
 
-  DEFINE_STATIC_LOCAL(
+  DEFINE_THREAD_SAFE_STATIC_LOCAL(
       CustomCountHistogram, objectSizeFreedByHeapCompaction,
-      ("BlinkGC.ObjectSizeFreedByHeapCompaction", 1, 4 * 1024 * 1024, 50));
+      new CustomCountHistogram("BlinkGC.ObjectSizeFreedByHeapCompaction", 1,
+                               4 * 1024 * 1024, 50));
   objectSizeFreedByHeapCompaction.count(m_freedSize / 1024);
 
 #if DEBUG_LOG_HEAP_COMPACTION_RUNNING_TIME