Improved KF insertion after fades to still.
Improved KF insertion after fades to still.

This code extends what was previously done for GFs, to pick
cases where insertion of a key frame after a fade (or other
transition or complex motion)  followed by a still section, will
be beneficial and will reduce the number of forced key frames.

Change-Id: If8bca00457f0d5f83dc3318a587f61c17d90f135

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