Apply the initial thread priority on the starting thread on Windows

Apply the initial thread priority on the starting thread on Windows

To remove a dependency to the thread handle on setting the initial
thread priority, change the logic to apply the initial thread priority
on the starting thread.

BUG=468793
Committed: https://crrev.com/0da84eb2bdb24a044412e5ba6e1f605d4cdbbe71
Cr-Commit-Position: refs/heads/master@{#336076}

[Takashi Toyoshima, 2015-06-24 06:35:21]

toyoshim@chromium.org changed reviewers:
+ gab@chromium.org, thestig@chromium.org

[Takashi Toyoshima, 2015-06-24 06:39:43]

PTAL.

[Lei Zhang, 2015-06-25 01:53:35]

lgtm

[Takashi Toyoshima, 2015-06-25 02:28:49]

The CQ bit was checked by toyoshim@chromium.org

[commit-bot: I haz the power, 2015-06-25 02:29:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1199313004/20001

[commit-bot: I haz the power, 2015-06-25 02:34:16]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-06-25 02:35:10]

Patchset 2 (id:??) landed as
https://crrev.com/0da84eb2bdb24a044412e5ba6e1f605d4cdbbe71
Cr-Commit-Position: refs/heads/master@{#336076}

[gab, 2015-06-25 14:48:00]

lgtm