Update bisect script to handle deleted .DEPS.git from chromium source

Fix issues caused due to GitMigration.

BUG=
NOTRY=True

Committed: https://crrev.com/ccfc9db1828f746c54df5dfbbc6494bb0fd05c40
Cr-Commit-Position: refs/heads/master@{#291909}

[prasadv, 2014-08-26 07:46:03]

prasadv@chromium.org changed reviewers:
+ qyearsley@chromium.org, tonyg@chromium.org

[prasadv, 2014-08-26 07:46:03]

Update bisect script to handle deleted .DEPS.git from chromium source
.DEPS.git file from src/ is deleted as a part of GitMigration.
Made necessary changes in bisect and related modules to handle this change.
To handle backward compatibility, we still check for .DEPS.git first and if it
is not found fallback to DEPS.

BUG= 407171
NOTRY=true

[tonyg, 2014-08-26 15:30:33]

lgtm

[tonyg, 2014-08-26 15:31:03]

ps. The need for better unittesting here is becoming more and more apparent...

[tonyg, 2014-08-26 15:37:16]

The CQ bit was checked by tonyg@chromium.org

[commit-bot: I haz the power, 2014-08-26 15:38:01]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/prasadv@chromium.org/503283002/40001

[commit-bot: I haz the power, 2014-08-26 15:38:41]

Committed patchset #3 (40001) as f33542728c6ae741894d4ead745a9178b39ec5ce

[commit-bot: I haz the power, 2014-09-10 02:43:01]

Patchset 3 (id:??) landed as
https://crrev.com/ccfc9db1828f746c54df5dfbbc6494bb0fd05c40
Cr-Commit-Position: refs/heads/master@{#291909}