android: Remove RenderWidgetHostViewAndroid's pointer to ContentViewCore when swapped

The change from https://codereview.chromium.org/26753005/ is causing crashes
due to unclear lifetimes of ContentViewCore with respect to 
RenderWidgetHostViewAndroid.  In this patch, we remove the pointer from
RWHV to CVC when RWHV is swapped out.

BUG=324341

Review URL: https://codereview.chromium.org/149753008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250525 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250525
Record how often people manually override the blocking SSL warning

We should know how often people manually override the blocking SSL warning. Adds another UMA stat to track that.

BUG=none

Review URL: https://codereview.chromium.org/134003005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250526 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250526