Don't crash when granting permissions to active tab.
It seems unlikely for active tab permissions to be granted to a tab that
is closing but on the other hand there is nothing that would prevent a
race condition in which the RenderView is destroyed before the
ExtensionMsg_UpdateTabSpecificPermissions message is processed.
The ExtensionMsg_{Update,Clear}TabSpecificPermissions message is changed
to a ROUTED message so that it is sent to the specific RenderView directly.
This removes the need to find the RenderView by tab_id which could fail.
BUG=396232
Review URL: https://codereview.chromium.org/708713003
Cr-Commit-Position: refs/heads/master@{#304784}
9 files changed
