
Make getActiveElement() on Tooltip public.

Use case:
- I am writing a goog.ui.Component with multiple children
- I attach a single shared tooltip to each child
- The parent component wants to show a different tooltip based on which
child is active.

It seems here cleaner to give the parent knowledge of which child the
tooltip refers to, than to create a tooltip subclass knowledge of the
element -> data mapping.  In my case, I am also rendering the tooltip
contents within a goog.ui.Component and just using the Tooltip for the
behavior, so with this change I can avoid subclassing Tooltip.

R=eae
DELTA=1  (0 added, 1 deleted, 0 changed)


Revision created by MOE tool push_codebase.
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git-svn-id: 35241bd708fe29f1f6c7a4322d322e99ff93b95e@267 0b95b8e8-c90f-11de-9d4f-f947ee5921c8

johan/closure-library,johan/closure-library,johan/closure-library