Factor our mChildrenChanged from doTransaction

We are trying to eliminate the whole doTransaction traversal. Following
queued-transaction changes we can update various values on flinger
directly rather than in-directing through the main-thread.

Test: Existing tests pass. simpleperf
Bug: 186200583
Change-Id: I0536f889602ce0801e9f79881bbe1adb7b163d46
4 files changed