DevTools: add instrumentation for deferred canvas rasterization

Source/core/inspector/InspectorInstrumentation.cpp

Index: Source/core/inspector/InspectorInstrumentation.cpp
diff --git a/Source/core/inspector/InspectorInstrumentation.cpp b/Source/core/inspector/InspectorInstrumentation.cpp
index d05984a3b29cb7e861144978aef63589d973ecd1..2fb2a4853b6c9601fa73d4a7a2b6bc0b33184abd 100644
--- a/Source/core/inspector/InspectorInstrumentation.cpp
+++ b/Source/core/inspector/InspectorInstrumentation.cpp
@@ -236,12 +236,14 @@ const char ImageDecodeTask[] = "ImageDecodeTask";
 const char Paint[] = "Paint";
 const char Layer[] = "Layer";
 const char BeginFrame[] = "BeginFrame";
+const char UpdateLayer[] = "UpdateLayer";
 };
 
 namespace InstrumentationEventArguments {
 const char LayerId[] = "layerId";
-const char PageId[] = "pageId";
+const char LayerTreeId[] = "layerTreeId";
 const char NodeId[] = "nodeId";
+const char PageId[] = "pageId";
 };
 
 InstrumentingAgents* instrumentationForPage(Page* page)