Prevent webview reuse

 Bug: 4742007
 Bug: 4770356
 Also pipe all loadUrl's through Tab so that it can immediately
 update its internal state. This is necessary as javascript:
 uris do not cause onPageStarted/finished callbacks to happen,
 thus the url and title of the Tab do not update.

Change-Id: I6d17e8627db505eaa9158339fdfc7afd2c6672a2
4 files changed