Makes GetComponentExtensionResourceManager() thread-safe.

Makes GetComponentExtensionResourceManager() thread-safe.

As is noted in a bug, this method can be called on various thread.
Actually, the instance itself holds simple mapping and its method
can be const, therefore it's safer to early-initialize and the
method just returns the already initialized object.

Also this should be const and the method does not change its
internal state, therefore it's thread safe.

BUG=445747
R=yoz@chromium.org
TEST=no functional changes / build succeeds

Committed: https://crrev.com/ee458c9161f034acde693bc6823d18b6845472c3
Cr-Commit-Position: refs/heads/master@{#310029}

[Jun Mukai, 2015-01-05 23:10:50]

yoz, are you back?  Could you take a look?

[Yoyo Zhou, 2015-01-06 00:50:46]

LGTM

https://chromiumcodereview.appspot.com/830833002/diff/20001/extensions/shell/...
File extensions/shell/browser/shell_extensions_browser_client.h (right):

https://chromiumcodereview.appspot.com/830833002/diff/20001/extensions/shell/...
extensions/shell/browser/shell_extensions_browser_client.h:75:
GetComponentExtensionResourceManager() override;
nit: this looks odd, is it clang-formatted correctly?

[Jun Mukai, 2015-01-06 01:16:50]

https://chromiumcodereview.appspot.com/830833002/diff/20001/extensions/shell/...
File extensions/shell/browser/shell_extensions_browser_client.h (right):

https://chromiumcodereview.appspot.com/830833002/diff/20001/extensions/shell/...
extensions/shell/browser/shell_extensions_browser_client.h:75:
GetComponentExtensionResourceManager() override;
On 2015/01/06 00:50:46, Yoyo Zhou wrote:
> nit: this looks odd, is it clang-formatted correctly?

This is the output of clang-format actually.
with "const", GetComponentExtensionResourceManager() can't fit into the previous
line.

[Jun Mukai, 2015-01-06 01:17:00]

The CQ bit was checked by mukai@chromium.org

[commit-bot: I haz the power, 2015-01-06 01:18:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/830833002/20001

[commit-bot: I haz the power, 2015-01-06 01:31:02]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-01-06 01:31:58]

Patchset 2 (id:??) landed as
https://crrev.com/ee458c9161f034acde693bc6823d18b6845472c3
Cr-Commit-Position: refs/heads/master@{#310029}