Reland of Don't bother running realpath in DeviceUtils._GetChangedAndStaleFiles()

Reland of Don't bother running realpath in DeviceUtils._GetChangedAndStaleFiles() (patchset #2 id:40001 of https://codereview.chromium.org/1306883004/ )

Reason for revert:
- Now has realpath behaviour removed from md5sum.
- Now md5sum.py detects when it should re-push an out-of-date binary.

BUG=520082
Committed: https://crrev.com/a25d597f08a3b6ccd4020f9400e092842b563744
Cr-Commit-Position: refs/heads/master@{#346396}

[agrieve, 2015-08-27 03:25:12]

Created Reland of Don't bother running realpath in
DeviceUtils._GetChangedAndStaleFiles()

[agrieve, 2015-08-27 13:47:33]

On 2015/08/27 03:25:12, agrieve wrote:
> Created Reland of Don't bother running realpath in
> DeviceUtils._GetChangedAndStaleFiles()

Note: this now also depends on https://codereview.chromium.org/1321503003, which
adds md5sum binary updating when pushing.

[jbudorick, 2015-08-28 18:38:06]

lgtm

[agrieve, 2015-08-31 15:22:36]

The CQ bit was checked by agrieve@chromium.org

[commit-bot: I haz the power, 2015-08-31 15:22:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1307393004/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1307393004/40001

[commit-bot: I haz the power, 2015-08-31 16:28:03]

Committed patchset #2 (id:40001)

[commit-bot: I haz the power, 2015-08-31 16:28:41]

Patchset 2 (id:??) landed as
https://crrev.com/a25d597f08a3b6ccd4020f9400e092842b563744
Cr-Commit-Position: refs/heads/master@{#346396}