Reland "Mandoline filesystem: Build the filesystem on windows."

Reland "Mandoline filesystem: Build the filesystem on windows."

This adds a cast which gcc didn't need, but msvc-64 wants. This condition
is checked for overflow at the top of the method.

BUG=490237
First Review URL: https://codereview.chromium.org/1163713002
TBR=sky@chromium.org

Committed: https://crrev.com/655f1b18105cb2afe0ba166a75da1477d2194661
Cr-Commit-Position: refs/heads/master@{#332436}

[Elliot Glaysher, 2015-06-02 17:55:30]

erg@chromium.org changed reviewers:
+ sky@chromium.org

[Elliot Glaysher, 2015-06-02 17:56:07]

tbring two line windows 64 specific compile change to already reviewed code.

[Elliot Glaysher, 2015-06-02 17:56:14]

The CQ bit was checked by erg@chromium.org

[commit-bot: I haz the power, 2015-06-02 17:57:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1166763002/20001

[commit-bot: I haz the power, 2015-06-02 18:41:29]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-06-02 18:43:28]

Patchset 2 (id:??) landed as
https://crrev.com/655f1b18105cb2afe0ba166a75da1477d2194661
Cr-Commit-Position: refs/heads/master@{#332436}