DevTools: DOMStorage should notify the view about storage modifications instead of DOMStorageModel

R=apavlov, pfeldman, vsevik

Review URL: https://chromiumcodereview.appspot.com/22346003

git-svn-id: svn://svn.chromium.org/blink/trunk@156635 bbb929c8-8fbe-4397-9dbb-9b2b20218538