Avoid double-removing prerender alias URLs.

The initial alias URL gets another reference when creating a MatchComplete
replacement, but subsequent URLs are just copied over. Remove them from the
original (soon to be deleted) prerender so their ownership is moved to the
MatchComplete.

BUG=none

Review URL: https://codereview.chromium.org/180183007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253922 0039d316-1c4b-4281-b951-d872f2087c98
EventSender: Allow modifiers to be set for wheel events

BUG=289887

Review URL: https://codereview.chromium.org/183473002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253923 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253923