Aura overlay scrollbars shouldn't invalidate thumb on scroll or enabled state.

third_party/WebKit/Source/platform/scroll/ScrollbarTestSuite.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ScrollbarTestSuite_h
 #define ScrollbarTestSuite_h
 
 #include "platform/heap/GarbageCollected.h"
 #include "platform/scroll/ScrollableArea.h"
 #include "platform/scroll/Scrollbar.h"
@@ skipping 16 matching lines @@
     MockScrollableArea* mock = create();
     mock->setMaximumScrollOffset(maximumScrollOffset);
     return mock;
   }
 
   MOCK_CONST_METHOD0(visualRectForScrollbarParts, LayoutRect());
   MOCK_CONST_METHOD0(isActive, bool());
   MOCK_CONST_METHOD1(scrollSize, int(ScrollbarOrientation));
   MOCK_CONST_METHOD0(isScrollCornerVisible, bool());
   MOCK_CONST_METHOD0(scrollCornerRect, IntRect());
-  MOCK_CONST_METHOD0(horizontalScrollbar, Scrollbar*());
-  MOCK_CONST_METHOD0(verticalScrollbar, Scrollbar*());
   MOCK_CONST_METHOD0(enclosingScrollableArea, ScrollableArea*());
   MOCK_CONST_METHOD1(visibleContentRect, IntRect(IncludeScrollbarsInRect));
   MOCK_CONST_METHOD0(contentsSize, IntSize());
   MOCK_CONST_METHOD0(scrollableAreaBoundingBox, IntRect());
   MOCK_CONST_METHOD0(layerForHorizontalScrollbar, GraphicsLayer*());
   MOCK_CONST_METHOD0(layerForVerticalScrollbar, GraphicsLayer*());
+  MOCK_CONST_METHOD0(horizontalScrollbar, Scrollbar*());
+  MOCK_CONST_METHOD0(verticalScrollbar, Scrollbar*());
 
   bool userInputScrollable(ScrollbarOrientation) const override { return true; }
   bool scrollbarsCanBeActive() const override { return true; }
   bool shouldPlaceVerticalScrollbarOnLeft() const override { return false; }
   void updateScrollOffset(const ScrollOffset& offset, ScrollType) override {
     m_scrollOffset = offset.shrunkTo(m_maximumScrollOffset);
   }
   IntSize scrollOffsetInt() const override {
     return flooredIntSize(m_scrollOffset);
   }
   IntSize minimumScrollOffsetInt() const override { return IntSize(); }
   IntSize maximumScrollOffsetInt() const override {
     return expandedIntSize(m_maximumScrollOffset);
   }
   int visibleHeight() const override { return 768; }
   int visibleWidth() const override { return 1024; }
   bool scrollAnimatorEnabled() const override { return false; }
   int pageStep(ScrollbarOrientation) const override { return 0; }
   void scrollControlWasSetNeedsPaintInvalidation() {}
 
   using ScrollableArea::horizontalScrollbarNeedsPaintInvalidation;
   using ScrollableArea::verticalScrollbarNeedsPaintInvalidation;
   using ScrollableArea::clearNeedsPaintInvalidationForScrollControls;
 
   DEFINE_INLINE_VIRTUAL_TRACE() { ScrollableArea::trace(visitor); }
 
+ protected:
+  explicit MockScrollableArea() : m_maximumScrollOffset(ScrollOffset(0, 100)) {}
+  explicit MockScrollableArea(const ScrollOffset& offset)
+      : m_maximumScrollOffset(offset) {}
+
  private:
   void setMaximumScrollOffset(const ScrollOffset& maximumScrollOffset) {
     m_maximumScrollOffset = maximumScrollOffset;
   }
 
-  explicit MockScrollableArea() : m_maximumScrollOffset(ScrollOffset(0, 100)) {}
-
   ScrollOffset m_scrollOffset;
   ScrollOffset m_maximumScrollOffset;
 };
 
 class ScrollbarTestSuite : public testing::Test {
  public:
   ScrollbarTestSuite() {}
 
   void SetUp() override {
     TestingPlatformSupport::Config config;
     config.compositorSupport = Platform::current()->compositorSupport();
     m_fakePlatform =
         WTF::makeUnique<TestingPlatformSupportWithMockScheduler>(config);
   }
 
   void TearDown() override { m_fakePlatform = nullptr; }
 
  private:
   std::unique_ptr<TestingPlatformSupportWithMockScheduler> m_fakePlatform;
 };
 
 }  // namespace blink
 
 #endif