Fix JSON serialization of PerformanceEntry subclasses

third_party/WebKit/Source/core/timing/PerformanceRenderTiming.cpp

Index: third_party/WebKit/Source/core/timing/PerformanceRenderTiming.cpp
diff --git a/third_party/WebKit/Source/core/timing/PerformanceRenderTiming.cpp b/third_party/WebKit/Source/core/timing/PerformanceRenderTiming.cpp
index 6e1ae535f9a4ad6fbec53637f647f074c01e551d..997748b5151cca8ffaf07dcdfd02d632884d0baa 100644
--- a/third_party/WebKit/Source/core/timing/PerformanceRenderTiming.cpp
+++ b/third_party/WebKit/Source/core/timing/PerformanceRenderTiming.cpp
@@ -31,6 +31,7 @@
 
 #include "core/timing/PerformanceRenderTiming.h"
 
+#include "bindings/core/v8/V8ObjectBuilder.h"
 #include "core/dom/Document.h"
 #include "core/loader/DocumentLoader.h"
 
@@ -58,6 +59,12 @@ unsigned PerformanceRenderTiming::sourceFrame() const
     return m_sourceFrame;
 }
 
+void PerformanceRenderTiming::buildJSONValue(V8ObjectBuilder& builder) const
+{
+    PerformanceEntry::buildJSONValue(builder);
+    builder.addNumber("sourceFrame", sourceFrame());
+}
+
 DEFINE_TRACE(PerformanceRenderTiming)
 {
     visitor->trace(m_requestingDocument);