X87: Debugger: use debug break slots to break at function exit.

X87: Debugger: use debug break slots to break at function exit.

port fc9c5275c3a747caca709b7d5745579f70e61301 (r29672).

original commit message:

    Debugger: use debug break slots to break at function exit.

    By not having to patch the return sequence (we patch the debug
    break slot right before it), we don't overwrite it and therefore
    don't have to keep the original copy of the code around.

BUG=

Committed: https://crrev.com/1d9216504965ab4f3e88d99b4f07bdbefa305676
Cr-Commit-Position: refs/heads/master@{#29694}

[chunyang.dai, 2015-07-16 08:16:48]

Patchset #1 (id:1) has been deleted

[chunyang.dai, 2015-07-16 08:17:14]

chunyang.dai@intel.com changed reviewers:
+ weiliang.lin@intel.com

[chunyang.dai, 2015-07-16 08:17:14]

PTAL

[Weiliang, 2015-07-16 08:26:17]

The CQ bit was checked by weiliang.lin@intel.com

[Weiliang, 2015-07-16 08:26:17]

lgtm

[commit-bot: I haz the power, 2015-07-16 08:26:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1236023007/20001

[commit-bot: I haz the power, 2015-07-16 08:49:39]

Committed patchset #1 (id:20001)

[commit-bot: I haz the power, 2015-07-16 08:49:50]

Patchset 1 (id:??) landed as
https://crrev.com/1d9216504965ab4f3e88d99b4f07bdbefa305676
Cr-Commit-Position: refs/heads/master@{#29694}