Add main thread scrolling reasons to GraphicsLayer::layerTreeAsJSON.

third_party/WebKit/Source/platform/graphics/GraphicsLayerDebugInfo.cpp

Index: third_party/WebKit/Source/platform/graphics/GraphicsLayerDebugInfo.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/GraphicsLayerDebugInfo.cpp b/third_party/WebKit/Source/platform/graphics/GraphicsLayerDebugInfo.cpp
index 417aac87d1d16c30e926cc9534f80a240178629b..72a425682ce427601a1fc9b9f10f31ad1392e042 100644
--- a/third_party/WebKit/Source/platform/graphics/GraphicsLayerDebugInfo.cpp
+++ b/third_party/WebKit/Source/platform/graphics/GraphicsLayerDebugInfo.cpp
@@ -20,6 +20,7 @@
 #include "platform/graphics/GraphicsLayerDebugInfo.h"
 
 #include "base/trace_event/trace_event_argument.h"
+#include "platform/scroll/MainThreadScrollingReason.h"
 
 namespace blink {
 
@@ -27,6 +28,7 @@ GraphicsLayerDebugInfo::GraphicsLayerDebugInfo()
     : m_compositingReasons(CompositingReasonNone)
     , m_squashingDisallowedReasons(SquashingDisallowedReasonsNone)
     , m_ownerNodeId(0)
+    , m_mainThreadScrollingReasons(0)
 {
 }
 
@@ -40,6 +42,7 @@ std::unique_ptr<base::trace_event::TracedValue> GraphicsLayerDebugInfo::asTraced
     appendCompositingReasons(tracedValue.get());
     appendSquashingDisallowedReasons(tracedValue.get());
     appendOwnerNodeId(tracedValue.get());
+    appendMainThreadScrollingReasons(tracedValue.get());
     return tracedValue;
 }
 
@@ -106,4 +109,9 @@ void GraphicsLayerDebugInfo::clearAnnotatedInvalidateRects()
     m_previousInvalidations.swap(m_invalidations);
 }
 
+void GraphicsLayerDebugInfo::appendMainThreadScrollingReasons(base::trace_event::TracedValue* tracedValue) const
+{
+    MainThreadScrollingReason::mainThreadScrollingReasonsAsTracedValue(m_mainThreadScrollingReasons, tracedValue);
+}
+
 } // namespace blink