Fix setCurrentPlayTime for started but not yet pulsed animations

Also fix the behavior for calling reverse() immediately after
start(). Such case now triggers end() right away, which is
consistent with what the animation would do in M.

Bug: 29271714
Change-Id: I045e36e039179a3c462f22bc6a3a765437de4074

core/java/android/animation/ValueAnimator.java

@@ -602,7 +602,9 @@ public class ValueAnimator extends Animator implements AnimationHandler.Animatio
         long currentTime = AnimationUtils.currentAnimationTimeMillis();
         mStartTime = currentTime - seekTime;
         mStartTimeCommitted = true; // do not allow start time to be compensated for jank
-        if (!mRunning) {
+        if (!isPulsingInternal()) {
+            // If the animation loop hasn't started, the startTime will be adjusted in the first
+            // frame based on seek fraction.
             mSeekFraction = fraction;
         }
         mOverallFraction = fraction;
@@ -980,6 +982,10 @@ public class ValueAnimator extends Animator implements AnimationHandler.Animatio
         mStarted = true;
         mPaused = false;
         mRunning = false;
+        // Resets mLastFrameTime when start() is called, so that if the animation was running,
+        // calling start() would put the animation in the
+        // started-but-not-yet-reached-the-first-frame phase.
+        mLastFrameTime = 0;
         AnimationHandler animationHandler = AnimationHandler.getInstance();
         animationHandler.addAnimationFrameCallback(this, (long) (mStartDelay * sDurationScale));
 
@@ -1095,7 +1101,7 @@ public class ValueAnimator extends Animator implements AnimationHandler.Animatio
      */
     @Override
     public void reverse() {
-        if (mRunning) {
+        if (isPulsingInternal()) {
             long currentTime = AnimationUtils.currentAnimationTimeMillis();
             long currentPlayTime = currentTime - mStartTime;
             long timeLeft = getScaledDuration() - currentPlayTime;
@@ -1103,6 +1109,7 @@ public class ValueAnimator extends Animator implements AnimationHandler.Animatio
             mStartTimeCommitted = true; // do not allow start time to be compensated for jank
             mReversing = !mReversing;
         } else if (mStarted) {
+            mReversing = !mReversing;
             end();
         } else {
             start(true);
@@ -1176,6 +1183,15 @@ public class ValueAnimator extends Animator implements AnimationHandler.Animatio
         }
     }
 
+    /**
+     * Internal only: This tracks whether the animation has gotten on the animation loop. Note
+     * this is different than {@link #isRunning()} in that the latter tracks the time after start()
+     * is called (or after start delay if any), which may be before the animation loop starts.
+     */
+    private boolean isPulsingInternal() {
+        return mLastFrameTime > 0;
+    }
+
     /**
      * Returns the name of this animator for debugging purposes.
      */