DevTools: Implement undo, redo operations for the DOMStorage views.

Source/core/inspector/InspectorDOMStorageAgent.cpp

Index: Source/core/inspector/InspectorDOMStorageAgent.cpp
diff --git a/Source/core/inspector/InspectorDOMStorageAgent.cpp b/Source/core/inspector/InspectorDOMStorageAgent.cpp
index 8656ada90f6451c89426239fb4d0e0f07ba49828..f076ea240df7ef8993c1c72797267ddd8b60f20c 100644
--- a/Source/core/inspector/InspectorDOMStorageAgent.cpp
+++ b/Source/core/inspector/InspectorDOMStorageAgent.cpp
@@ -106,6 +106,25 @@ void InspectorDOMStorageAgent::disable(ErrorString*)
     m_state->setBoolean(DOMStorageAgentState::domStorageAgentEnabled, false);
 }
 
+void InspectorDOMStorageAgent::getDOMStorageItem(ErrorString* errorString, const RefPtr<JSONObject>& storageId, const String& key, bool* exists, String* value)
+{
+    Frame* frame;
+    OwnPtr<StorageArea> storageArea = findStorageArea(errorString, storageId, frame);
+    if (!storageArea)
+        return;
+
+    ExceptionCode ec = 0;
+    *exists = storageArea->contains(key, ec, frame);
+    if (hadException(ec, errorString))
+        return;
+
+    if (*exists) {
+        ec = 0;

[apavlov, 2013/07/31 12:51:35]

This is not required, since hadException() would have returned true above.

+        *value = storageArea->getItem(key, ec, frame);
+        hadException(ec, errorString);
+    }
+}
+
 void InspectorDOMStorageAgent::getDOMStorageItems(ErrorString* errorString, const RefPtr<JSONObject>& storageId, RefPtr<TypeBuilder::Array<TypeBuilder::Array<String> > >& items)
 {
     Frame* frame;