Fix ViewEventTestBase for Win Aura, re-enable tests on Win.

Move ChromeViewsDelegate usage to ViewEventTestBase.
(previously just done in BookmarkBarViewEventTestBase)
(needed to create DesktopNativeWidgetAura widgets)
(otherwise NativeWidgetAura widgets DCHECK with no parent/context)
Cleanup SetUp()/TearDown for correctness and clarity.
Re-enable tests that pass locally with the above change:
BookmarkBarViewTest20.ContextMenuExitTest (except non-Aura Win)
ButtonDropDownDragTest.DragActivation
MenuItemViewTest*.*
MenuModelAdapterTest.RebuildMenu

These <tests> reliably pass locally with this patch applied.
interactive_ui_tests.exe --gtest_filter=<tests> --gtest_repeat=-1 --gtest_break_on_failure
They only break on locking the computer or using the mouse.

BUG=128724
TEST=NONE
R=pkasting@chromium.org,sky@chromium.org

Review URL: https://codereview.chromium.org/26567014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228854 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228854