Refactor the tab-loading animation

This change instead updates the animation progress in delta-time
increments, which prevents a bunch of clock math and rewinding of start
timestamps.

Bug: None
Change-Id: I6848e3c3ca2d7c844f56f126d72c9b8420364b2a
Reviewed-on: https://chromium-review.googlesource.com/c/1356261
Commit-Queue: Peter Boström <pbos@chromium.org>
Reviewed-by: Sidney San Martín <sdy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613161}

chrome/browser/ui/views/tabs/tab_icon.h

@@ -69,10 +69,15 @@ class TabIcon : public views::View {
   // last-painted state to know to redraw the final frame as the animation
   // finishes.
   struct LoadingAnimationState {
+    LoadingAnimationState();
+
     base::TimeDelta elapsed_time;
-    double loading_progress;
-    SkAlpha loading_progress_alpha;
-    double favicon_fade_in_progress;
+    base::Optional<double> loading_progress;
+    base::Optional<double> loading_progress_fade_out;
+    // TODO(pbos): Make this a type that can represent "not started" and "ended"
+    // separately. Right now the value 1.0 is used to indicate that the
+    // animation has ended (and we're not waiting for it to start).
+    base::Optional<double> favicon_fade_in_progress = 1.0;
   };
 
   // views::View:
@@ -94,10 +99,7 @@ class TabIcon : public views::View {
   // current tab state.
   void PaintLoadingAnimation(gfx::Canvas* canvas, const gfx::Rect& bounds);
 
-  void UpdateLoadingAnimationState();
-  LoadingAnimationState GetLoadingAnimationState() const;
-
-  void RewindLoadingProgressTimerIfNecessary(double progress);
+  void UpdatePendingAnimationState();
 
   // Returns false if painting the loading animation would paint the same thing
   // that's already painted.
@@ -171,13 +173,9 @@ class TabIcon : public views::View {
   // Loading progress used for drawing the progress indicator.
   double target_loading_progress_ = 1.0;
 
+  base::TimeTicks last_animation_update_time_;
   LoadingAnimationState animation_state_;
-
-  base::Optional<base::TimeTicks> loading_progress_timer_;
-
-  // Fade-in animation for the favicon. Starts when a favicon loads or the tab
-  // is no longer loading. The latter case will fade into a placeholder icon.
-  base::Optional<base::TimeTicks> favicon_fade_in_animation_;
+  LoadingAnimationState pending_animation_state_;
 
   // Crash animation (in place of favicon). Lazily created since most of the
   // time it will be unneeded.

chrome/browser/ui/views/tabs/tab_unittest.cc

@@ -143,7 +143,10 @@ class FakeTabController : public TabController {
 
 class TabTest : public ChromeViewsTestBase {
  public:
-  TabTest() {}
+  TabTest() {
+    // Prevent the fake clock from starting at 0 which is the null time.
+    fake_clock_.Advance(base::TimeDelta::FromMilliseconds(2000));
+  }
   ~TabTest() override {}
 
   static TabIcon* GetTabIcon(const Tab& tab) { return tab.icon_; }
@@ -312,7 +315,8 @@ class TabTest : public ChromeViewsTestBase {
     // Forward the clock enough for any running animations to finish.
     DCHECK(icon->clock_ == &fake_clock_);
     fake_clock_.Advance(base::TimeDelta::FromMilliseconds(2000));
-    icon->UpdateLoadingAnimationState();
+    icon->StepLoadingAnimation(icon->waiting_state_.elapsed_time);
+    icon->animation_state_ = icon->pending_animation_state_;
   }
 
   static float GetLoadingProgress(TabIcon* icon) {
@@ -650,6 +654,7 @@ TEST_F(TabTest, LayeredThrobber) {
   // Reset.
   data.network_state = TabNetworkState::kNone;
   tab.SetData(data);
+  FinishRunningLoadingAnimations(icon);
   EXPECT_FALSE(icon->ShowingLoadingAnimation());
 
   // Simulate a drag started and stopped during a load: layer painting stops
@@ -668,6 +673,7 @@ TEST_F(TabTest, LayeredThrobber) {
   EXPECT_TRUE(icon->layer());
   data.network_state = TabNetworkState::kNone;
   tab.SetData(data);
+  FinishRunningLoadingAnimations(icon);
   EXPECT_FALSE(icon->ShowingLoadingAnimation());
 
   // Simulate a tab load starting and stopping during tab dragging (or with
@@ -679,6 +685,7 @@ TEST_F(TabTest, LayeredThrobber) {
   EXPECT_FALSE(icon->layer());
   data.network_state = TabNetworkState::kNone;
   tab.SetData(data);
+  FinishRunningLoadingAnimations(icon);
   EXPECT_FALSE(icon->ShowingLoadingAnimation());
 }