Move WebMouseWheelEvent into its own header file.

chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper_unit_test.mm

 // Copyright 2013 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.
 
 #import "chrome/browser/renderer_host/chrome_render_widget_host_view_mac_history_swiper.h"
 
 #include "base/mac/scoped_nsobject.h"
 #import "base/mac/sdk_forward_declarations.h"
 #import "chrome/browser/ui/cocoa/test/cocoa_test_helper.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/WebKit/public/platform/WebInputEvent.h"
+#include "third_party/WebKit/public/platform/WebMouseWheelEvent.h"
 #import "third_party/ocmock/OCMock/OCMock.h"
 #import "third_party/ocmock/ocmock_extensions.h"
 
 @interface HistorySwiper (MacHistorySwiperTest)
 - (BOOL)systemSettingsAllowHistorySwiping:(NSEvent*)event;
 - (BOOL)browserCanNavigateInDirection:
         (history_swiper::NavigationDirection)forward
                                 event:(NSEvent*)event;
 - (void)removeHistoryOverlay;
 - (void)showHistoryOverlay:(history_swiper::NavigationDirection)direction;
@@ skipping 516 matching lines @@
 
   scrollEvent =
       scrollWheelEventWithPhase(NSEventPhaseChanged, NSEventPhaseNone, 0, 20);
   [historySwiper_ handleEvent:scrollEvent];
   [historySwiper_ handleEvent:scrollWheelEventWithPhase(NSEventPhaseEnded)];
   sendEndGestureEventAtPoint(makePoint(0.5, 0.7));
 
   // Vertical motion should never trigger a history swipe!
   EXPECT_FALSE(magic_mouse_history_swipe_);
 }