DevTools: add "Jump to Relayout Boundary" context menu item in Elements panel

Source/core/inspector/InspectorDOMAgent.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2009 Joseph Pecoraro
  *
  * 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
@@ skipping 1964 matching lines @@
     Node* node = m_backendIdToNode.get(backendNodeId).first;
     String nodeGroup = m_backendIdToNode.get(backendNodeId).second;
     *nodeId = pushNodePathToFrontend(node);
 
     if (nodeGroup == "") {
         m_backendIdToNode.remove(backendNodeId);
         m_nodeGroupToBackendIdMap.find(nodeGroup)->value.remove(node);
     }
 }
 
+void InspectorDOMAgent::getRelayoutBoundary(ErrorString* errorString, int nodeId, int* relayoutBoundaryNodeId)
+{
+    Node* node = assertNode(errorString, nodeId);
+    if (!node)
+        return;
+    RenderObject* renderer = node->renderer();
+    if (!renderer) {
+        *errorString = "No renderer for node, perhaps orphan or hidden node";
+        return;
+    }
+    while (renderer && !renderer->isRoot() && !renderer->isRelayoutBoundaryForInspector())
+        renderer = renderer->container();
+    Node* resultNode = renderer ? renderer->generatingNode() : node->ownerDocument();
+    *relayoutBoundaryNodeId = pushNodePathToFrontend(resultNode);
+}
+
 PassRefPtr<TypeBuilder::Runtime::RemoteObject> InspectorDOMAgent::resolveNode(Node* node, const String& objectGroup)
 {
     Document* document = node->isDocumentNode() ? &node->document() : node->ownerDocument();
     Frame* frame = document ? document->frame() : 0;
     if (!frame)
         return 0;
 
     InjectedScript injectedScript = m_injectedScriptManager->injectedScriptFor(mainWorldScriptState(frame));
     if (injectedScript.hasNoValue())
         return 0;
 
     return injectedScript.wrapNode(node, objectGroup);
 }
 
 } // namespace WebCore