Route Scroll events through a cc::InputHandler

ui/views/controls/scrollbar/scrollbar_unittest.cc

Index: ui/views/controls/scrollbar/scrollbar_unittest.cc
diff --git a/ui/views/controls/scrollbar/scrollbar_unittest.cc b/ui/views/controls/scrollbar/scrollbar_unittest.cc
index 75196bdef824697db693a50cdb17bcfeb2c843c8..356d9f440c96aed69d5c3d72febda9366ccf3c2a 100644
--- a/ui/views/controls/scrollbar/scrollbar_unittest.cc
+++ b/ui/views/controls/scrollbar/scrollbar_unittest.cc
@@ -33,6 +33,8 @@ class TestScrollBarController : public views::ScrollBarController {
     return 10;
   }
 
+  void OnScrollEventFromScrollBar(ui::ScrollEvent* event) override {}
+
   // We save the last values in order to assert the correctness of the scroll
   // operation.
   views::ScrollBar* last_source;