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

LayoutTests/inspector/storage-panel-dom-storage-undo-redo-expected.txt

+This test checks the undo/redo operations are performed correctly on the DOM storage views
+
+
+Running: initialize
+Initialized localStorage and sessionStorage by clearing entries
+
+Running: undoLocalStorageWithEmptyStack
+LocalStorage contents:[]
+
+Running: redoLocalStorageWithEmptyStack
+LocalStorage contents:[]
+
+Running: addLocalStorageEntries
+LocalStorage contents:[a1=b1,a2=b2]
+
+Running: undoLocalStorageLastAddition
+LocalStorage contents:[a1=b1]
+
+Running: undoSessionStorageWithEmptyStack
+SessionStorage contents:[]
+
+Running: redoSessionStorageWithEmptyStack
+SessionStorage contents:[]
+
+Running: undoLocalStorageBeyondBounds

[apavlov, 2013/08/02 08:16:59]

This looks strange. At this point, you should still have a single undo entry for
the a1=b1 addition in the stack... You are undoing 2 actions, right? Perhaps
worth adding a message into the output? WDYT?

+LocalStorage contents:[]
+
+Running: addSessionStorageEntries
+SessionStorage contents:[p1=q1,p2=q2,p3=q3,p4=q4]
+
+Running: redoLocalStorageBeyondBounds
+LocalStorage contents:[a1=b1,a2=b2]

[apavlov, 2013/08/02 08:16:59]

Same thing - 2 actions redone?

+
+Running: undoSessionStorageLastAddition
+SessionStorage contents:[p1=q1,p2=q2,p3=q3]
+
+Running: modifyLocalStorageValues
+LocalStorage contents:[a1=x1,a2=x2]
+
+Running: undoLocalStorageModifications
+LocalStorage contents:[a1=b1,a2=b2]
+
+Running: redoSessionStorageLastAddition
+SessionStorage contents:[p1=q1,p2=q2,p3=q3,p4=q4]
+
+Running: redoLocalStorageModifications
+LocalStorage contents:[a1=x1,a2=x2]
+
+Running: modifySessionStorageEntriesKey

[apavlov, 2013/08/02 08:16:59]

Adding a test for undo of the key modifications would be nice.

+SessionStorage contents:[m1=q1,m2=q2,m3=q3,m4=q4]
+
+Running: undoLocalStorageModifications
+LocalStorage contents:[a1=b1,a2=b2]
+