Move the last-focused and last-mouse-event pepper plugin instance variable from RenderFrame back to RenderView.

I moved this in r238191, but as Nasko pointed out this will break once there are multiple RenderFrames per RenderView. So instead I'm moving them back for now. Once RenderView is gone, the browser will know which frame is in focus, and the IPCs which use thse variables now will go to the right RenderFrame. At that point these variables can move back again.

BUG=304341
R=nasko@chromium.org

Review URL: https://codereview.chromium.org/105713002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238979 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238979