Update mach_override to upstream 1a1bb352

CFLog, which is overridden by content/renderer/renderer_main_platform_delegate_mac.mm, contains the following instruction in 64-bit form on 10.6.8 and 10.7.5:

4881ECD0000000                  sub        rsp, 0xd0

mach_override’s puny simplistic fake disassembler didn’t understand this instruction. This resulted in mach_override failing, which triggered a CHECK failure during renderer startup, with the result that everything would be a sad tab on 10.6 and 10.7 64-bit.

The latest version of mach_override replaces its weak old non-disassembler with libudis86, which should be much more capable in the area of understanding instructions, and which should improve mach_override’s ability to patch code without always having to retrain it.

In the mean time, the upstream change that was probably causing us to be unable to update to the current HEAD (https://github.com/rentzsch/mach_star/commit/498e0ba3)
has been backed out since then (https://github.com/rentzsch/mach_override/commit/1b3aa46f), so it should now be safe to update to HEAD.

Local patches https://codereview.chromium.org/21208002/ and https://codereview.chromium.org/22798004/ have been reapplied with minor fixes to work with the current version.

BUG=315218
R=avi@chromium.org

Review URL: https://codereview.chromium.org/61273002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233175 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233175