Include compositing reasons in the "debug" GraphicsLayer tree dump.

Source/platform/graphics/GraphicsLayer.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 707 matching lines @@
         if (m_hasScrollParent) {
             writeIndent(ts, indent + 1);
             ts << "(hasScrollParent 1)\n";
         }
         if (m_hasClipParent) {
             writeIndent(ts, indent + 1);
             ts << "(hasClipParent 1)\n";
         }
     }
 
+    if (flags & LayerTreeIncludesDebugInfo) {
+        writeIndent(ts, indent + 1);
+        ts << "(compositingReasons\n";
+        for (size_t i = 0; i < WTF_ARRAY_LENGTH(compositingReasonStringMap); ++i) {
+            if (m_debugInfo.compositingReasons() & compositingReasonStringMap[i].reason) {
+                writeIndent(ts, indent + 2);
+                ts << compositingReasonStringMap[i].description << "\n";
+            }
+        }
+        writeIndent(ts, indent + 1);
+        ts << ")\n";
+    }
+
     if (m_children.size()) {
         writeIndent(ts, indent + 1);
         ts << "(children " << m_children.size() << "\n";
 
         unsigned i;
         for (i = 0; i < m_children.size(); i++)
             m_children[i]->dumpLayer(ts, indent + 2, flags, renderingContextMap);
         writeIndent(ts, indent + 1);
         ts << ")\n";
     }
@@ skipping 486 matching lines @@
 #ifndef NDEBUG
 void showGraphicsLayerTree(const WebCore::GraphicsLayer* layer)
 {
     if (!layer)
         return;
 
     String output = layer->layerTreeAsText(WebCore::LayerTreeIncludesDebugInfo);
     fprintf(stderr, "%s\n", output.utf8().data());
 }
 #endif