Don't hard-code python path.

Recently upgraded Macs have Python 2.7 in /usr/local/bin and the
hard-coded path is breaking the compile step.

R=mark@chromium.org
BUG=304948

Review URL: https://codereview.chromium.org/27593003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229375 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229375
[rAC, OSX] Stop text flickering.

Stop animation overlay's message from jumping between centered and
left-aligned. (This happened due to sizing control to the exact text
size - it is now keeping its width).

BUG=308189
R=isherman@chromium.org

Review URL: https://codereview.chromium.org/27596002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229376 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229376