DevTools: CSSAgent::enable should report an error if DOM agent hasn't been enabled

Source/core/inspector/InspectorCSSAgent.cpp

 /*
  * Copyright (C) 2010, Google 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 435 matching lines @@
     m_nodeToInspectorStyleSheet.clear();
     m_documentToViaInspectorStyleSheet.clear();
     resetNonPersistentData();
 }
 
 void InspectorCSSAgent::resetNonPersistentData()
 {
     resetPseudoStates();
 }
 
-void InspectorCSSAgent::enable(ErrorString*, PassRefPtrWillBeRawPtr<EnableCallback> prpCallback)
+void InspectorCSSAgent::enable(ErrorString* errorString, PassRefPtrWillBeRawPtr<EnableCallback> prpCallback)
 {
+    if (!m_domAgent->enabled()) {
+        *errorString = "DOM agent needs to be enabled first.";

[yurys, 2014/10/15 09:29:11]

Why is that? Can you provide a test case? Should we automatically enable DOM
agent?

+        return;
+    }
     m_state->setBoolean(CSSAgentState::cssAgentEnabled, true);
     if (!m_pageAgent->resourceContentLoader()) {
         wasEnabled();
         prpCallback->sendSuccess();
         return;
     }
     m_pageAgent->resourceContentLoader()->ensureResourcesContentLoaded(new InspectorCSSAgent::InspectorResourceContentLoaderCallback(this, prpCallback));
 }
 
 void InspectorCSSAgent::wasEnabled()
@@ skipping 1004 matching lines @@
     visitor->trace(m_invalidatedDocuments);
     visitor->trace(m_nodeToInspectorStyleSheet);
     visitor->trace(m_documentToViaInspectorStyleSheet);
 #endif
     visitor->trace(m_inspectorUserAgentStyleSheet);
     InspectorBaseAgent::trace(visitor);
 }
 
 } // namespace blink