This CL fixes a bug that CursorAnchorInfoBuilder does't make a
copy if the Matrix specified with #setMatrix.
Without this fix, IMM#updateCursorAnchorInfo could fail to detect
duplicated events when the same instances of
CursorAnchorInfoBuilder and Matrix are reused to optimize
performance.
Change-Id: I50c50a12a06d3cda4dec445b171b61ceb78da21a