This CL adds one more functionality to CursorAnchorInfo
that enables applications to associate the composition
string with its positional information. This is useful
for an IME to handle CursorAnchorInfo asynchronously.
This is also useful for the framework to detect if
the application is unnecessarily calling
IMM#updateCursorAnchroInfo with duplicate event.
BUG: 14579622
Change-Id: Ie75c17b523dad33e97b08c15f5f5267573ce2063
81f4cb3f85