Handle sync changes on the Start Page tiles while context menus are showing.

Handle sync changes on the Start Page tiles while context menus are showing.

This handles the case where
SearchResultTileItemView::SetSearchResult(SearchResult*) may be called
from a nested run loop while its context menu is showing. This cancels
the menu (it's for the old item).

BUG=462470
TEST=Right-click on a start page app to get its context menu. On another
machine (with the same profile), uninstall the app. Context menu should
disappear. Chrome shouldn't crash.

Committed: https://crrev.com/b7f4866c0a046daf3d836ee058edddf4905d30af
Cr-Commit-Position: refs/heads/master@{#318844}

[tapted, 2015-03-02 23:04:39]

tapted@chromium.org changed reviewers:
+ calamity@chromium.org

[calamity, 2015-03-03 00:48:30]

lgtm, thanks for diagnosing and fixing.

[tapted, 2015-03-03 06:11:44]

Thanks Chris! finally got around to verifying the fix works as intended - it
does \o/

[tapted, 2015-03-03 06:11:50]

The CQ bit was checked by tapted@chromium.org

[commit-bot: I haz the power, 2015-03-03 06:13:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/969953002/1

[commit-bot: I haz the power, 2015-03-03 06:22:23]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-03 06:23:25]

Patchset 1 (id:??) landed as
https://crrev.com/b7f4866c0a046daf3d836ee058edddf4905d30af
Cr-Commit-Position: refs/heads/master@{#318844}