Don't offset the position of the thumbnail in change transitions

There are two adaptors used for change transitions: mAdapter and
mThumbnailAdapter. The position and crop of the leashe in the
adapters are adjusted to the start bounds when the a transition
starts, and currently the same value is used for mAdapter and
mThumbnailAdapter. The problem here is, as the thumbnail is a child
of the window of |mAdapter|, the thumbnail gets double offseted
incrrectly, which results in the snapshot being shown at an
incorrect position until the client starts the animation and
modifies the position.

This CL lets RemoteAnimationController give each adapter its
explicit start bounds.

Bug: 159294946
Test: No buffer jump in change transitions anymore.
Change-Id: I1dafd5587ed7c9b628d8f1f40a2559ec3e9a63d5