Add an API to report debugName in GraphicsLayer

Source/core/platform/graphics/GraphicsLayerClient.h

Index: Source/core/platform/graphics/GraphicsLayerClient.h
diff --git a/Source/core/platform/graphics/GraphicsLayerClient.h b/Source/core/platform/graphics/GraphicsLayerClient.h
index ecc988816451668e98641cfab2b3c9d2ad88611d..1728b4394ba13ca3f0a3ecc87d1d0a6174859ea8 100644
--- a/Source/core/platform/graphics/GraphicsLayerClient.h
+++ b/Source/core/platform/graphics/GraphicsLayerClient.h
@@ -26,6 +26,8 @@
 #ifndef GraphicsLayerClient_h
 #define GraphicsLayerClient_h
 
+#include "wtf/text/WTFString.h"
+
 namespace WebCore {
 
 class FloatPoint;
@@ -78,6 +80,8 @@ public:
 
     virtual bool isTrackingRepaints() const { return false; }
 
+    virtual String debugName(const GraphicsLayer*) = 0;
+
 #ifndef NDEBUG
     // RenderLayerBacking overrides this to verify that it is not
     // currently painting contents. An ASSERT fails, if it is.