Towards moving guest management to chrome: Introduce GuestViewManager

This CL moves a lot of functionality from BrowserPluginGuestManager to GuestViewManager including instance ID allocation. 

Currently GuestViewManager is a BrowserPluginGuestManagerDelegate. 

In the future, GuestViewManager will completely replace BrowserPluginGuestManager. 

BUG=364141, 330264

Review URL: https://codereview.chromium.org/258373002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@268391 0039d316-1c4b-4281-b951-d872f2087c98
49 files changed