webui: Allow to show empty menus and let them ignore key operations.

Previously we use to prevent menu buttons from showing an empty menu because
sending key events to an empty menu causes to freeze. But we use an custom empty
menu in the new tab page. This CL lets menu buttons allow to show an empty menu
and lets the menu ignore the key operations to avoid the freeze.

BUG=305585
TEST=manually

Review URL: https://codereview.chromium.org/26789002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228109 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228109
Revert 227999 "Alternative workaround for mac kernel bug."

> Alternative workaround for mac kernel bug.
> 
> BUG=298276
> 
> Review URL: https://codereview.chromium.org/25325002

This change seemed to cause the Mac ASAN bot to timeout when running
the ipc_tests.

TBR=hubbe@chromium.org

Review URL: https://codereview.chromium.org/26384003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228110 0039d316-1c4b-4281-b951-d872f2087c98
drive: Rewrite SearchMetadataTest to treat local IDs properly

Remove AddEntriesToMetadataFromCache, store cache files in AddEntriesToMetadata instead.

BUG=275270
TEST=unit_tests --gtest_filter="SearchMetadata*"
R=kinaba@chromium.org

Review URL: https://codereview.chromium.org/26792003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228111 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228111