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..bb038dd3bf42391054f834e5acaa2159363ce7b2 100644
--- a/third_party/WebKit/Source/platform/graphics/GraphicsLayerDebugInfo.cpp
+++ b/third_party/WebKit/Source/platform/graphics/GraphicsLayerDebugInfo.cpp
@@ -20,6 +20,9 @@
 #include "platform/graphics/GraphicsLayerDebugInfo.h"
 
 #include "base/trace_event/trace_event_argument.h"
+#include "platform/scroll/MainThreadScrollingReason.h"
+
+#include <vector>
 
 namespace blink {
 
@@ -27,6 +30,7 @@ GraphicsLayerDebugInfo::GraphicsLayerDebugInfo()
     : m_compositingReasons(CompositingReasonNone)
     , m_squashingDisallowedReasons(SquashingDisallowedReasonsNone)
     , m_ownerNodeId(0)
+    , m_mainThreadScrollingReasons(0)
 {
 }
 
@@ -40,6 +44,7 @@ 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 +111,15 @@ void GraphicsLayerDebugInfo::clearAnnotatedInvalidateRects()
     m_previousInvalidations.swap(m_invalidations);
 }
 
+void GraphicsLayerDebugInfo::appendMainThreadScrollingReasons(base::trace_event::TracedValue* tracedValue) const
+{
+    std::vector<std::string> reasons = MainThreadScrollingReason::mainThreadScrollingReasonsAsStringArray(m_mainThreadScrollingReasons);
+    size_t arraySize = reasons.size();
+    tracedValue->BeginArray("main_thread_scrolling_reasons");
+    for (size_t i = 0; i < arraySize; ++i) {
+        tracedValue->AppendString(reasons[i]);
+    }
+    tracedValue->EndArray();
+}
+
 } // namespace blink