Move ScrollableArea timer to TaskRunnerTimer.

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

Index: third_party/WebKit/Source/platform/scroll/ScrollbarTestSuite.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollbarTestSuite.h b/third_party/WebKit/Source/platform/scroll/ScrollbarTestSuite.h
index cd0402a80e48371e7ff9c5b74fb41f18f6243d89..7b499d50e748312e9c669db9051b70927f660083 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollbarTestSuite.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollbarTestSuite.h
@@ -9,6 +9,9 @@
 #include "platform/scroll/ScrollableArea.h"
 #include "platform/scroll/Scrollbar.h"
 #include "platform/scroll/ScrollbarThemeMock.h"
+#include "public/platform/Platform.h"
+#include "public/platform/WebScheduler.h"
+#include "public/platform/WebThread.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "wtf/PtrUtil.h"
 #include <memory>
@@ -61,6 +64,10 @@ class MockScrollableArea : public GarbageCollectedFinalized<MockScrollableArea>,
   int pageStep(ScrollbarOrientation) const override { return 0; }
   void scrollControlWasSetNeedsPaintInvalidation() {}
 
+  RefPtr<WebTaskRunner> getTimerTaskRunner() const final {
+    return Platform::current()->currentThread()->scheduler()->timerTaskRunner();
+  }
+
   using ScrollableArea::horizontalScrollbarNeedsPaintInvalidation;
   using ScrollableArea::verticalScrollbarNeedsPaintInvalidation;
   using ScrollableArea::clearNeedsPaintInvalidationForScrollControls;