Enumerate HID devices asynchronously on Windows.

Enumerate HID devices asynchronously on Windows.

Avoid possibly long blocking times in the Windows SetupDi function
calls made to enumerate devices by offloading to the FILE thread.
Now that we can be sure that a stray request to the device won't
block the UI additional calls to get the device's product and serial
number strings can be made.

BUG=457899
Committed: https://crrev.com/8c5a2c5f3c9efbc0c5810e8269d788210175a6af
Cr-Commit-Position: refs/heads/master@{#316939}

[Reilly Grant (use Gerrit), 2015-02-18 00:16:11]

reillyg@chromium.org changed reviewers:
+ rockot@chromium.org

[Reilly Grant (use Gerrit), 2015-02-18 00:16:12]

Ken, please take a look at this patch.

[Ken Rockot(use gerrit already), 2015-02-18 20:40:23]

lgtm

https://codereview.chromium.org/936603003/diff/1/device/hid/hid_service_win.h
File device/hid/hid_service_win.h (right):

https://codereview.chromium.org/936603003/diff/1/device/hid/hid_service_win.h...
device/hid/hid_service_win.h:42: static void InitialEnumerationFileThread(
nit: Judging from its ubiquity across the codebase I would suggest that an
idiomatic suffix would be "OnFileThread" for this method (and AddDevice...
below).

On a related note, I'd hesitate to use any non-accessor method name that isn't a
verb phrase. Would this be OK as EnumerateOnFileThread? Or maybe
DoFirstEnumerationOnFileThread if you think the "initial" qualification is
important?

[Reilly Grant (use Gerrit), 2015-02-18 20:58:19]

New patchsets have been uploaded after l-g-t-m from rockot@chromium.org

[Reilly Grant (use Gerrit), 2015-02-18 20:58:35]

The CQ bit was checked by reillyg@chromium.org

[commit-bot: I haz the power, 2015-02-18 20:59:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/936603003/20001

[commit-bot: I haz the power, 2015-02-19 00:53:09]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-02-19 00:53:59]

Patchset 2 (id:??) landed as
https://crrev.com/8c5a2c5f3c9efbc0c5810e8269d788210175a6af
Cr-Commit-Position: refs/heads/master@{#316939}