Remove rotation and use flag useIdentityTransform for screenshots.

There's a lot of confusing logic where 90 and 270 rotation values need
to be flipped to ensure the screenshot is taken the correct orientation.
There's also confusion what useIdentityTransform means, especially if a
non 0 rotation value is sent.

The cases screenshot cares about is the following:
1. Take screenshot in current display orientation
2. Take screenshot with 0 rotation so the caller can handle rotating the
screenshot themselves.

With these two cases in mind, remove the rotation value passed in for
screenshots. If useIdentityTransform is true, it will rotate the
screenshot so it's in the 0 orientation. If useIdentityTransform is
false, it will use the current display rotation.

This simplifies the caller logic since they no longer have to find the
current display rotation to ensure the screenshot is taken in the
current rotation. The callers can just request the screenshot with
useIdentityTransform set to false.

Test: adb shell screencap
Test: Power + volume screenshot
Test: Screen rotation
Fixes: 135942984
Change-Id: I3435ee8b5dac05e910ec1e695f398c5dcdcff9e9