Pass the physical scroll delta through the scroll customization path.

third_party/WebKit/Source/web/tests/TopControlsTest.cpp

 /*
  * Copyright (C) 2015 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 330 matching lines @@
     // Initialize top controls to be shown.
     webView->setTopControlsHeight(50.f, true);
     webView->topControls().setShownRatio(1);
 
     webView->topControls().scrollBegin();
     EXPECT_FLOAT_EQ(50.f, webView->topControls().contentOffset());
 
     // This will result in a 20px scroll to the top controls so the show ratio
     // will be 30/50 == 0.6 which is not representible in a float. Make sure
     // that scroll still consumes the whole delta.
-    FloatSize remainingDelta = webView->topControls().scrollBy(FloatSize(0, -10));
+    FloatSize remainingDelta = webView->topControls().scrollBy(FloatSize(0, 10));
     EXPECT_EQ(0, remainingDelta.height());
 }
 
 // Scrollable subregions should scroll before top controls
 TEST_F(TopControlsTest, MAYBE(ScrollableSubregionScrollFirst))
 {
     WebViewImpl* webView = initialize("overflow-scrolling.html");
     webView->setTopControlsHeight(50.f, true);
     webView->topControls().setShownRatio(1);
     frame()->view()->scrollableArea()->setScrollPosition(IntPoint(0, 50), ProgrammaticScroll);
@@ skipping 363 matching lines @@
     // that's 1600px wide so the minimum scale is 0.25 to encompass that.
     ASSERT_EQ(0.25f, webView->minimumPageScaleFactor());
 
     // The viewport will match the layout width at scale=0.5 so the height used
     // for vh should be (300 / 0.5) for the layout height + (100 / 0.5) for top
     // controls = 800.
     EXPECT_EQ(800, frame()->view()->viewportSizeForViewportUnits().height());
 }
 
 } // namespace blink