Send the WebMouseWheelEvents unconverted if Shift is down.

ui/events/blink/web_input_event_builders_win.cc

 // 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.
 
 #include "ui/events/blink/web_input_event_builders_win.h"
 
 #include "ui/display/win/screen_win.h"
 #include "ui/events/blink/blink_event_util.h"
 #include "ui/events/event_utils.h"
 
@@ skipping 285 matching lines @@
     // Currently we leave hasPreciseScrollingDeltas false, even for trackpad
     // scrolls that generate WM_MOUSEWHEEL, since we don't have a good way to
     // distinguish these from real mouse wheels (crbug.com/545234).
     wheel_delta = static_cast<float>(GET_WHEEL_DELTA_WPARAM(wparam));
 
     if (message == WM_MOUSEHWHEEL) {
       horizontal_scroll = true;
       wheel_delta = -wheel_delta;  // Windows is <- -/+ ->, WebKit <- +/- ->.
     }
   }
-  if (key_state & MK_SHIFT)
-    horizontal_scroll = true;
 
   // Set modifiers based on key state.
   result.modifiers =
       ui::EventFlagsToWebEventModifiers(ui::GetModifiersFromKeyState());
   if (key_state & MK_SHIFT)
     result.modifiers |= WebInputEvent::ShiftKey;
   if (key_state & MK_CONTROL)
     result.modifiers |= WebInputEvent::ControlKey;
   if (key_state & MK_LBUTTON)
     result.modifiers |= WebInputEvent::LeftButtonDown;
@@ skipping 49 matching lines @@
     result.wheelTicksX = wheel_delta;
   } else {
     result.deltaY = scroll_delta;
     result.wheelTicksY = wheel_delta;
   }
 
   return result;
 }
 
 }  // namespace ui