Actually wait until the display is ready.

When this was rewritten to only wait for display state changes and not
brightness changes, it forgot to take into account whether a change was
already in flight when reporting whether a change was happening. Fix
that so the display appropriately reports when it's ready and when it's
blocked.

Bug: 32559368
Test: Take systrace of device wakeup, see it actually waits until the
      display is actually ready

Change-Id: Ie3bd5c48d109a0fb2628ccc8f67bb52be51fad5c

services/core/java/com/android/server/display/DisplayPowerState.java

@@ -369,8 +369,8 @@ final class DisplayPowerState {
                     mPendingBacklight = backlight;
 
                     boolean changeInProgress = mStateChangeInProgress || mBacklightChangeInProgress;
-                    mStateChangeInProgress = stateChanged;
-                    mBacklightChangeInProgress = backlightChanged;
+                    mStateChangeInProgress = stateChanged || mStateChangeInProgress;
+                    mBacklightChangeInProgress = backlightChanged || mBacklightChangeInProgress;
 
                     if (!changeInProgress) {
                         mLock.notifyAll();