Adds browser-side component of Java Bridge for a TabContents

This patch adds JavaBridgeDispatcherHostManager, which co-ordinates injecting
Java objects into all RenderViews corresponding to a TabContents. The class is
owned by TabContents and manages one instance of JavaBridgeDispatcherHost for
each RenderViewHost.

Also adds TabContentsObserver::RenderViewDeleted().

BUG=96703

Review URL: http://codereview.chromium.org/8366034

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@107085 0039d316-1c4b-4281-b951-d872f2087c98
7 files changed