Add UMA metrics for root scroller intervention to track forcing passive breakage.

third_party/WebKit/Source/core/testing/Internals.cpp

Index: third_party/WebKit/Source/core/testing/Internals.cpp
diff --git a/third_party/WebKit/Source/core/testing/Internals.cpp b/third_party/WebKit/Source/core/testing/Internals.cpp
index 33b5df0e89dd0152b0f46cfba0eb594ae0df6aa9..0c252c2947baf31e0a641d918ee9bad6ef69cb69 100644
--- a/third_party/WebKit/Source/core/testing/Internals.cpp
+++ b/third_party/WebKit/Source/core/testing/Internals.cpp
@@ -128,6 +128,7 @@
 #include "core/workers/WorkerThread.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
 #include "platform/Cursor.h"
+#include "platform/Histogram.h"
 #include "platform/Language.h"
 #include "platform/PlatformKeyboardEvent.h"
 #include "platform/RuntimeEnabledFeatures.h"
@@ -386,6 +387,16 @@ void Internals::clearHitTestCache(Document* doc, ExceptionState& exceptionState)
     doc->layoutViewItem().clearHitTestCache();
 }
 
+int Internals::histogramCount(const String& name, int bucket, ExceptionState& exceptionState) const
+{
+    int32_t count;
+    if (!EnumerationHistogram::GetHistogramCount(name.utf8().data(), bucket, &count)) {
+        exceptionState.throwDOMException(InvalidAccessError, "Could not find histogram");
+        return 0;
+    }
+    return count;
+}
+
 bool Internals::isPreloaded(const String& url)
 {
     return isPreloadedBy(url, contextDocument());