Fix math errors causing black screen. DO NOT MERGE

Turning off animations in the Developer options creates a ValueAnimator
duration scale of 0. This is used as the denominator in RampAnimator
which, if the numerator is also 0, sets mAnimatedValue to NaN. Rounding
NaN to the nearest int produces 0 which is then assigned to
mScreenBrightness in DisplayPowerState.

A copy mistake which assigned mTransitionAnimationScale as the default
value for mAnimatorDurationScale in WindowManagerService is also
fixed here.

Bug 7515609 fixed.

Change-Id: I39f8d0a7abdd5a1fe70d757fe95fbddaf7a0ed51

Author: Craig Mautner

services/java/com/android/server/power/RampAnimator.java

@@ -102,20 +102,26 @@ public void run() {
             final long frameTimeNanos = mChoreographer.getFrameTimeNanos();
             final float timeDelta = (frameTimeNanos - mLastFrameTimeNanos)
                     * 0.000000001f;
-            final float amount = timeDelta * mRate / ValueAnimator.getDurationScale();
             mLastFrameTimeNanos = frameTimeNanos;
 
             // Advance the animated value towards the target at the specified rate
             // and clamp to the target. This gives us the new current value but
             // we keep the animated value around to allow for fractional increments
             // towards the target.
-            int oldCurrentValue = mCurrentValue;
-            if (mTargetValue > mCurrentValue) {
-                mAnimatedValue = Math.min(mAnimatedValue + amount, mTargetValue);
+            final float scale = ValueAnimator.getDurationScale();
+            if (scale == 0) {
+                // Animation off.
+                mAnimatedValue = mTargetValue;
             } else {
-                mAnimatedValue = Math.max(mAnimatedValue - amount, mTargetValue);
+                final float amount = timeDelta * mRate / scale;
+                if (mTargetValue > mCurrentValue) {
+                    mAnimatedValue = Math.min(mAnimatedValue + amount, mTargetValue);
+                } else {
+                    mAnimatedValue = Math.max(mAnimatedValue - amount, mTargetValue);
+                }
             }
-            mCurrentValue = (int)Math.round(mAnimatedValue);
+            final int oldCurrentValue = mCurrentValue;
+            mCurrentValue = Math.round(mAnimatedValue);
 
             if (oldCurrentValue != mCurrentValue) {
                 mProperty.setValue(mObject, mCurrentValue);

services/java/com/android/server/wm/WindowManagerService.java

@@ -821,7 +821,7 @@ private WindowManagerService(Context context, PowerManagerService pm,
         mTransitionAnimationScale = Settings.Global.getFloat(context.getContentResolver(),
                 Settings.Global.TRANSITION_ANIMATION_SCALE, mTransitionAnimationScale);
         setAnimatorDurationScale(Settings.Global.getFloat(context.getContentResolver(),
-                Settings.Global.ANIMATOR_DURATION_SCALE, mTransitionAnimationScale));
+                Settings.Global.ANIMATOR_DURATION_SCALE, mAnimatorDurationScale));
 
         // Track changes to DevicePolicyManager state so we can enable/disable keyguard.
         IntentFilter filter = new IntentFilter();