cc: Fix animation end value for animations that alternate direction

This fixes the logic used in Animation::TrimTimeToCurrentIteration for
times that are >= the total duration of the animation and animations
that alternate direction. The previous logic reversed the result from
the correct value, causing flicker at the end of such animations.

BUG=348071

Review URL: https://codereview.chromium.org/263243003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@268392 0039d316-1c4b-4281-b951-d872f2087c98

cc/animation/animation.cc

@@ -197,7 +197,7 @@ double Animation::TrimTimeToCurrentIteration(double monotonic_time) const {
 
   // If we are past the active interval, return iteration duration.
   if (is_past_total_duration) {
-    iteration = iterations_;
+    iteration = iterations_ - 1;
     trimmed = curve_->Duration();
   } else {
     iteration = static_cast<int>(trimmed / curve_->Duration());

cc/animation/animation_unittest.cc

@@ -60,26 +60,76 @@ TEST(AnimationTest, TrimTimeReverse) {
   EXPECT_EQ(0.75, anim->TrimTimeToCurrentIteration(1.25));
 }
 
-TEST(AnimationTest, TrimTimeAlternate) {
+TEST(AnimationTest, TrimTimeAlternateInfiniteIterations) {
   scoped_ptr<Animation> anim(CreateAnimation(-1));
   anim->set_direction(Animation::Alternate);
-  EXPECT_EQ(0, anim->TrimTimeToCurrentIteration(0.0));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(0.0));
   EXPECT_EQ(0.25, anim->TrimTimeToCurrentIteration(0.25));
   EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(0.5));
   EXPECT_EQ(0.75, anim->TrimTimeToCurrentIteration(0.75));
-  EXPECT_EQ(1, anim->TrimTimeToCurrentIteration(1.0));
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(1.0));
+  EXPECT_EQ(0.75, anim->TrimTimeToCurrentIteration(1.25));
+}
+
+TEST(AnimationTest, TrimTimeAlternateOneIteration) {
+  scoped_ptr<Animation> anim(CreateAnimation(1));
+  anim->set_direction(Animation::Alternate);
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(0.0));
+  EXPECT_EQ(0.25, anim->TrimTimeToCurrentIteration(0.25));
+  EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(0.5));
+  EXPECT_EQ(0.75, anim->TrimTimeToCurrentIteration(0.75));
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(1.0));
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(1.25));
+}
+
+TEST(AnimationTest, TrimTimeAlternateTwoIterations) {
+  scoped_ptr<Animation> anim(CreateAnimation(2));
+  anim->set_direction(Animation::Alternate);
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(0.0));
+  EXPECT_EQ(0.25, anim->TrimTimeToCurrentIteration(0.25));
+  EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(0.5));
+  EXPECT_EQ(0.75, anim->TrimTimeToCurrentIteration(0.75));
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(1.0));
   EXPECT_EQ(0.75, anim->TrimTimeToCurrentIteration(1.25));
+  EXPECT_EQ(0.25, anim->TrimTimeToCurrentIteration(1.75));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(2.0));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(2.25));
 }
 
-TEST(AnimationTest, TrimTimeAlternateReverse) {
+TEST(AnimationTest, TrimTimeAlternateReverseInfiniteIterations) {
   scoped_ptr<Animation> anim(CreateAnimation(-1));
   anim->set_direction(Animation::AlternateReverse);
   EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(0.0));
   EXPECT_EQ(0.75, anim->TrimTimeToCurrentIteration(0.25));
   EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(0.5));
   EXPECT_EQ(0.25, anim->TrimTimeToCurrentIteration(0.75));
-  EXPECT_EQ(0, anim->TrimTimeToCurrentIteration(1.0));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(1.0));
+  EXPECT_EQ(0.25, anim->TrimTimeToCurrentIteration(1.25));
+}
+
+TEST(AnimationTest, TrimTimeAlternateReverseOneIteration) {
+  scoped_ptr<Animation> anim(CreateAnimation(1));
+  anim->set_direction(Animation::AlternateReverse);
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(0.0));
+  EXPECT_EQ(0.75, anim->TrimTimeToCurrentIteration(0.25));
+  EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(0.5));
+  EXPECT_EQ(0.25, anim->TrimTimeToCurrentIteration(0.75));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(1.0));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(1.25));
+}
+
+TEST(AnimationTest, TrimTimeAlternateReverseTwoIterations) {
+  scoped_ptr<Animation> anim(CreateAnimation(2));
+  anim->set_direction(Animation::AlternateReverse);
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(0.0));
+  EXPECT_EQ(0.75, anim->TrimTimeToCurrentIteration(0.25));
+  EXPECT_EQ(0.5, anim->TrimTimeToCurrentIteration(0.5));
+  EXPECT_EQ(0.25, anim->TrimTimeToCurrentIteration(0.75));
+  EXPECT_EQ(0.0, anim->TrimTimeToCurrentIteration(1.0));
   EXPECT_EQ(0.25, anim->TrimTimeToCurrentIteration(1.25));
+  EXPECT_EQ(0.75, anim->TrimTimeToCurrentIteration(1.75));
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(2.0));
+  EXPECT_EQ(1.0, anim->TrimTimeToCurrentIteration(2.25));
 }
 
 TEST(AnimationTest, TrimTimeStartTime) {