Revert "Make programmatic scrolls respect smooth scroll flag"

This reverts commit 95d1a35e.

Reason for revert: Lots of scroll tests are broken, see e.g. https://ci.chromium.org/p/chromium/builders/ci/Mac10.11%20Tests/35520

Original change's description:
> Make programmatic scrolls respect smooth scroll flag
> 
> Programmatic smooth scrolls should also be instant if the smooth scroll
> flag is explicitly disabled.
> 
> Bug: 944583
> Change-Id: I2ea2ec972a9a232644350eb994b55f04522a4ca1
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1536759
> Reviewed-by: Stephen McGruer <smcgruer@chromium.org>
> Commit-Queue: David Bokan <bokan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#644051}

TBR=bokan@chromium.org,smcgruer@chromium.org

Change-Id: I0af76ee378d5212c124f81cb50a9f494450015de
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 944583
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1539140Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644124}

third_party/blink/renderer/core/scroll/scrollable_area.cc

@@ -255,7 +255,7 @@ void ScrollableArea::ProgrammaticScrollHelper(const ScrollOffset& offset,
                                               bool is_sequenced_scroll) {
   CancelScrollAnimation();
 
-  if (scroll_behavior == kScrollBehaviorSmooth && ScrollAnimatorEnabled()) {
+  if (scroll_behavior == kScrollBehaviorSmooth) {
     GetProgrammaticScrollAnimator().AnimateToOffset(offset,
                                                     is_sequenced_scroll);
   } else {

third_party/blink/renderer/core/scroll/scrollable_area_test.cc

@@ -24,26 +24,8 @@ namespace blink {
 namespace {
 
 using testing::_;
-using testing::Mock;
 using testing::Return;
 
-class MockAnimatingScrollableArea : public MockScrollableArea {
- public:
-  static MockAnimatingScrollableArea* Create() {
-    return MakeGarbageCollected<MockAnimatingScrollableArea>();
-  }
-  static MockAnimatingScrollableArea* Create(
-      const ScrollOffset& maximum_scroll_offset) {
-    MockAnimatingScrollableArea* mock = Create();
-    mock->SetMaximumScrollOffset(maximum_scroll_offset);
-    return mock;
-  }
-  Scrollbar* HorizontalScrollbar() const override { return nullptr; }
-  Scrollbar* VerticalScrollbar() const override { return nullptr; }
-  MOCK_CONST_METHOD0(ScrollAnimatorEnabled, bool());
-  MOCK_METHOD0(ScheduleAnimation, bool());
-};
-
 class ScrollbarThemeWithMockInvalidation : public ScrollbarThemeMock {
  public:
   MOCK_CONST_METHOD0(ShouldRepaintAllPartsOnInvalidation, bool());
@@ -287,43 +269,6 @@ TEST_F(ScrollableAreaTest, ScrollableAreaDidScroll) {
   EXPECT_EQ(51, scrollable_area->ScrollOffsetInt().Height());
 }
 
-TEST_F(ScrollableAreaTest, ProgrammaticScrollRespectAnimatorEnabled) {
-  ScopedTestingPlatformSupport<TestingPlatformSupportWithMockScheduler>
-      platform;
-
-  MockAnimatingScrollableArea* scrollable_area =
-      MockAnimatingScrollableArea::Create(ScrollOffset(0, 100));
-
-  // Disable animations. Make sure an explicitly smooth programmatic scroll is
-  // instantly scrolled.
-  {
-    EXPECT_CALL(*scrollable_area, ScrollAnimatorEnabled())
-        .WillRepeatedly(Return(false));
-    EXPECT_CALL(*scrollable_area, ScheduleAnimation()).Times(0);
-
-    scrollable_area->SetScrollOffset(ScrollOffset(0, 100), kProgrammaticScroll,
-                                     kScrollBehaviorSmooth);
-
-    EXPECT_EQ(100, scrollable_area->GetScrollOffset().Height());
-  }
-
-  Mock::VerifyAndClearExpectations(scrollable_area);
-
-  // Enable animations. A smooth programmatic scroll should now schedule an
-  // animation rather than immediatley mutating the offset.
-  {
-    EXPECT_CALL(*scrollable_area, ScrollAnimatorEnabled())
-        .WillRepeatedly(Return(true));
-    EXPECT_CALL(*scrollable_area, ScheduleAnimation()).WillOnce(Return(true));
-
-    scrollable_area->SetScrollOffset(ScrollOffset(0, 50), kProgrammaticScroll,
-                                     kScrollBehaviorSmooth);
-
-    // Offset is unchanged.
-    EXPECT_EQ(100, scrollable_area->GetScrollOffset().Height());
-  }
-}
-
 // Scrollbars in popups shouldn't fade out since they aren't composited and thus
 // they don't appear on hover so users without a wheel can't scroll if they fade
 // out.

third_party/blink/renderer/core/scroll/scrollbar_test_suite.h

@@ -118,12 +118,11 @@ class MockScrollableArea : public GarbageCollectedFinalized<MockScrollableArea>,
     ScrollableArea::Trace(visitor);
   }
 
- protected:
+ private:
   void SetMaximumScrollOffset(const ScrollOffset& maximum_scroll_offset) {
     maximum_scroll_offset_ = maximum_scroll_offset;
   }
 
- private:
   ScrollOffset scroll_offset_;
   ScrollOffset maximum_scroll_offset_;
   Member<MockPlatformChromeClient> chrome_client_;