Retrieve bleeding edge push revision from trunk commit message.

This is part of moving towards an lkgr-push script and prepares the deprecation of the prepare push commit.

BUG=
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/169843002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19482 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Prepare push to trunk.  Now working on version 3.25.1.

R=danno@chromium.org
TBR=danno@chromium.org

Review URL: https://codereview.chromium.org/170283011

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19483 ce2b1a6d-e550-0410-aec6-3dcde31c8c00