Move WebMouseWheelEvent into its own header file.

third_party/WebKit/public/platform/WebMouseWheelEvent.h

+// 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.
+
+#ifndef WebMouseWheelEvent_h
+#define WebMouseWheelEvent_h
+
+#include "WebInputEvent.h"
+
+namespace blink {
+
+// See WebInputEvent.h for details why this pack is here.
+#pragma pack(push, 4)
+
+// WebMouseWheelEvent ---------------------------------------------------------
+
+class WebMouseWheelEvent : public WebMouseEvent {
+ public:
+  enum Phase {
+    PhaseNone = 0,
+    PhaseBegan = 1 << 0,
+    PhaseStationary = 1 << 1,
+    PhaseChanged = 1 << 2,
+    PhaseEnded = 1 << 3,
+    PhaseCancelled = 1 << 4,
+    PhaseMayBegin = 1 << 5,
+  };
+
+  float deltaX;
+  float deltaY;
+  float wheelTicksX;
+  float wheelTicksY;
+
+  float accelerationRatioX;
+  float accelerationRatioY;
+
+  // This field exists to allow BrowserPlugin to mark MouseWheel events as
+  // 'resent' to handle the case where an event is not consumed when first
+  // encountered; it should be handled differently by the plugin when it is
+  // sent for thesecond time. No code within Blink touches this, other than to
+  // plumb it through event conversions.
+  int resendingPluginId;
+
+  Phase phase;
+  Phase momentumPhase;
+
+  bool scrollByPage;
+  bool hasPreciseScrollingDeltas;
+
+  RailsMode railsMode;
+
+  // Whether the event is blocking, non-blocking, all event
+  // listeners were passive or was forced to be non-blocking.
+  DispatchType dispatchType;
+
+  WebMouseWheelEvent()
+      : WebMouseEvent(sizeof(WebMouseWheelEvent)),
+        deltaX(0.0f),
+        deltaY(0.0f),
+        wheelTicksX(0.0f),
+        wheelTicksY(0.0f),
+        accelerationRatioX(1.0f),
+        accelerationRatioY(1.0f),
+        resendingPluginId(-1),
+        phase(PhaseNone),
+        momentumPhase(PhaseNone),
+        scrollByPage(false),
+        hasPreciseScrollingDeltas(false),
+        railsMode(RailsModeFree),
+        dispatchType(Blocking) {}
+};
+#pragma pack(pop)
+
+}  // namespace blink
+
+#endif  // WebMouseWheelEvent_h