Update CompositorCC WebLayerTreeView usage for WebKit API change

Two changes:
1.) Use initialize() instead of create() for WebLayerTreeView
2.) Add (empty) overrides for new pure virtuals on WebLayerTreeViewClient

BUG=none


Review URL: http://codereview.chromium.org/9122020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@123585 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed