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

third_party/WebKit/Source/platform/Histogram.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef Histogram_h
 #define Histogram_h
 
 #include "base/metrics/histogram_base.h"
 #include "platform/PlatformExport.h"
 #include "wtf/CurrentTime.h"
@@ skipping 17 matching lines @@
 };
 
 class PLATFORM_EXPORT BooleanHistogram : public CustomCountHistogram {
 public:
     BooleanHistogram(const char* name);
 };
 
 class PLATFORM_EXPORT EnumerationHistogram : public CustomCountHistogram {
 public:
     EnumerationHistogram(const char* name, base::HistogramBase::Sample boundaryValue);
+
+    static bool GetHistogramCount(const char* name, base::HistogramBase::Sample bucket, int32_t* count);

[Ilya Sherman, 2016/07/11 18:52:31]

I'd recommend adding a "ForTesting" suffix to any functions that you end up
adding to this file that should be used only in tests.

 };
 
 class PLATFORM_EXPORT SparseHistogram {
 public:
     explicit SparseHistogram(const char* name);
 
     void sample(base::HistogramBase::Sample);
 
 private:
     base::HistogramBase* m_histogram;
@@ skipping 26 matching lines @@
 // }
 // This macro records all times between 0us and 10 seconds.
 // Do not change this macro without renaming all metrics that use it!
 #define SCOPED_BLINK_UMA_HISTOGRAM_TIMER(name) \
 DEFINE_STATIC_LOCAL(CustomCountHistogram, scopedUsCounter, (name, 0, 10000000, 50)); \
 ScopedUsHistogramTimer timer(scopedUsCounter);
 
 } // namespace blink
 
 #endif // Histogram_h