Cleanup: Move code common in ChromeClient JavaScript dialog functions to a function template.

Cleanup: Move common code of ChromeClient JavaScript dialog functions to a function template.

- Changes the argument order of ChromeClient::
  runBeforeUnloadConfirmPanelInternal() for consistency with other functions
- Make notifyPopupOpeningObservers() public
- This CL adds notifyPopupOpeningObservers() call to ChromeClient::
  runBeforeUnloadConfirmPanel().  It should be harmless.

BUG=495378
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=196285

[tkent, 2015-06-02 03:22:53]

tkent@chromium.org changed reviewers:
+ yosin@chromium.org

[tkent, 2015-06-02 03:22:53]

yosin@, please review this.

[yosin_UTC9, 2015-06-02 05:07:40]

lgtm

Variadic template is so powerful!

[yosin_UTC9, 2015-06-02 05:07:44]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2015-06-02 05:08:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1162263007/1

[commit-bot: I haz the power, 2015-06-02 05:12:26]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=196285