Keep expanded if mouse moves off of scrollbar while dragging

cc/input/scrollbar_animation_controller_thinning_unittest.cc

Index: cc/input/scrollbar_animation_controller_thinning_unittest.cc
diff --git a/cc/input/scrollbar_animation_controller_thinning_unittest.cc b/cc/input/scrollbar_animation_controller_thinning_unittest.cc
index e1a1aa3cd53a5b79aafd9cd8c544d86f539232cf..a04c13ec59cc4bb54ded6c63d6c3ba6f82f7b84f 100644
--- a/cc/input/scrollbar_animation_controller_thinning_unittest.cc
+++ b/cc/input/scrollbar_animation_controller_thinning_unittest.cc
@@ -386,5 +386,143 @@ TEST_F(ScrollbarAnimationControllerThinningTest, MouseNearThenOver) {
   EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->thumb_thickness_scale_factor());
 }
 
+// First move the pointer on the scrollbar, then press it, then away and move

[bokan, 2016/09/23 00:39:12]

what do you mean by "move down"?

+// down. Confirm that the bar gets thick and dark. Then mouse up. Confirm that
+// the bar gets thickness and light.

[bokan, 2016/09/23 00:39:12]

Nit: thickness->thin

+TEST_F(ScrollbarAnimationControllerThinningTest,
+       MouseCaptureAndReleaseOutOfBar) {
+  base::TimeTicks time;
+
+  // Move in
+  scrollbar_controller_->DidMouseMoveNear(0);
+
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(0.7f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(0.4f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  // Should animate to thickened and darkened.
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(0.8f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(0.6f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  time += base::TimeDelta::FromSeconds(1);

[bokan, 2016/09/23 00:39:12]

We're overfitting here. Changing the animation curve means this test will fail.
It's fine to just jump ahead to the end and check the final state is as
expected. (also, how come the animation lasts 4 seconds? That's much longer than
in reality, no?)

[chaopeng, 2016/09/23 00:54:57]

I have tried jump 5 seconds but cannot get the expect. 
The "4 second" is from this field 
https://cs.chromium.org/chromium/src/cc/input/scrollbar_animation_controller....

[bokan, 2016/09/23 18:06:31]

Ah, got it, the duration is set specifically for the test in SetUp(). Could you
make that a global constant in this file and use that. Also, please look into
why just jumping ahead 4 seconds doesn't work, other tests in this file seem to
do that. gdb should be helpful here and is quite easy with cc_unittests as it
loads quickly (at least compared to chrome/webkit_tests).

+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(0.9f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(0.8f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  // Capture
+  scrollbar_controller_->DidCaptureScrollbarBegin();
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  // move away from bar.
+  scrollbar_controller_->DidMouseMoveNear(26);
+
+  // test for 10 seconds, stay thick and dark
+  for (int i = 0; i < 10; ++i) {
+    time += base::TimeDelta::FromSeconds(1);
+    scrollbar_controller_->Animate(time);
+    EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->Opacity());
+    EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->thumb_thickness_scale_factor());
+  }
+
+  // release
+  scrollbar_controller_->DidCaptureScrollbarEnd();
+
+  // get thickness and light
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(0.9f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(0.8f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(0.8f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(0.6f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(0.7f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(0.4f, scrollbar_layer_->thumb_thickness_scale_factor());
+}
+
+// First move the pointer on the scrollbar, then press it, then away and move
+// down. Confirm that the bar gets thick and dark. Then move point on the
+// scrollbar and mouse up. Confirm that the bar gets thick and dark.
+TEST_F(ScrollbarAnimationControllerThinningTest, MouseCaptureAndReleaseOnBar) {
+  base::TimeTicks time;
+
+  // Move in
+  scrollbar_controller_->DidMouseMoveNear(0);
+
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(0.7f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(0.4f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  // Should animate to thickened and darkened.
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(0.8f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(0.6f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(0.9f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(0.8f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  // Capture
+  scrollbar_controller_->DidCaptureScrollbarBegin();
+  time += base::TimeDelta::FromSeconds(1);
+  scrollbar_controller_->Animate(time);
+  EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->Opacity());
+  EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->thumb_thickness_scale_factor());
+
+  // move away from bar.
+  scrollbar_controller_->DidMouseMoveNear(26);
+
+  // test for 10 seconds, stay thick and dark
+  for (int i = 0; i < 10; ++i) {
+    time += base::TimeDelta::FromSeconds(1);
+    scrollbar_controller_->Animate(time);

[bokan, 2016/09/23 00:39:12]

I'd add some DidMouseMoveNear calls here to make sure they don't change anything
either.

+    EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->Opacity());
+    EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->thumb_thickness_scale_factor());
+  }
+
+  // move to the bar.
+  scrollbar_controller_->DidMouseMoveNear(0);
+
+  // release
+  scrollbar_controller_->DidCaptureScrollbarEnd();
+
+  // stay thick and dark
+  // test for 10 seconds, stay thick and dark
+  for (int i = 0; i < 10; ++i) {
+    time += base::TimeDelta::FromSeconds(1);
+    scrollbar_controller_->Animate(time);
+    EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->Opacity());
+    EXPECT_FLOAT_EQ(1.0f, scrollbar_layer_->thumb_thickness_scale_factor());
+  }
+}
+
 }  // namespace
 }  // namespace cc