layout-tests: Add flag for including compositingReasons in layerTreeAsText().

Source/platform/graphics/GraphicsLayer.cpp

Index: Source/platform/graphics/GraphicsLayer.cpp
diff --git a/Source/platform/graphics/GraphicsLayer.cpp b/Source/platform/graphics/GraphicsLayer.cpp
index d8884ed1cf32ccf04f1cc257901784c1cc9d3f51..e994c3a804483c437a466ef9a926becc8e0386cf 100644
--- a/Source/platform/graphics/GraphicsLayer.cpp
+++ b/Source/platform/graphics/GraphicsLayer.cpp
@@ -701,14 +701,13 @@ PassRefPtr<JSONObject> GraphicsLayer::layerTreeAsJSON(LayerTreeFlags flags, Rend
             json->setBoolean("hasClipParent", true);
     }
 
-    if (flags & LayerTreeIncludesDebugInfo) {
-        RefPtr<JSONArray> compositingReasonsJSON = adoptRef(new JSONArray);
-        for (size_t i = 0; i < kNumberOfCompositingReasons; ++i) {
-            if (m_debugInfo.compositingReasons() & kCompositingReasonStringMap[i].reason)
-                compositingReasonsJSON->pushString(kCompositingReasonStringMap[i].description);
-        }
-        json->setArray("compositingReasons", compositingReasonsJSON);
+    bool debug = flags & LayerTreeIncludesDebugInfo;
+    RefPtr<JSONArray> compositingReasonsJSON = adoptRef(new JSONArray);
+    for (size_t i = 0; i < kNumberOfCompositingReasons; ++i) {
+        if (m_debugInfo.compositingReasons() & kCompositingReasonStringMap[i].reason)
+            compositingReasonsJSON->pushString(debug ? kCompositingReasonStringMap[i].description : kCompositingReasonStringMap[i].shortName);
     }
+    json->setArray("compositingReasons", compositingReasonsJSON);
 
     if (m_children.size()) {
         RefPtr<JSONArray> childrenJSON = adoptRef(new JSONArray);