Avoid using !OS() constructs.

Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 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 534 matching lines @@
         hideSelectPopup();
     }
 
     if (m_pagePopup && pagePopup && m_pagePopup->hasSamePopupClient(pagePopup.get())) {
         // That click triggered a page popup that is the same as the one we just closed.
         // It needs to be closed.
         closePagePopup(m_pagePopup.get());
     }
 
     // Dispatch the contextmenu event regardless of if the click was swallowed.
+#if OS(WIN)
     // On Windows, we handle it on mouse up, not down.
-#if OS(MACOSX)
+#elif OS(MACOSX)
     if (event.button == WebMouseEvent::ButtonRight
         || (event.button == WebMouseEvent::ButtonLeft
             && event.modifiers & WebMouseEvent::ControlKey))
         mouseContextMenu(event);
-#elif OS(POSIX)
+#else
     if (event.button == WebMouseEvent::ButtonRight)
         mouseContextMenu(event);
 #endif
 }
 
 void WebViewImpl::mouseContextMenu(const WebMouseEvent& event)
 {
     if (!mainFrameImpl() || !mainFrameImpl()->frameView())
         return;
 
@@ skipping 358 matching lines @@
         return false;
 
     EventHandler* handler = frame->eventHandler();
     if (!handler)
         return keyEventDefault(event);
 
 #if !OS(MACOSX)
     const WebInputEvent::Type contextMenuTriggeringEventType =
 #if OS(WIN)
         WebInputEvent::KeyUp;
-#elif OS(POSIX)
+#else
         WebInputEvent::RawKeyDown;
 #endif
 
     bool isUnmodifiedMenuKey = !(event.modifiers & WebInputEvent::InputModifiers) && event.windowsKeyCode == VKEY_APPS;
     bool isShiftF10 = event.modifiers == WebInputEvent::ShiftKey && event.windowsKeyCode == VKEY_F10;
     if ((isUnmodifiedMenuKey || isShiftF10) && event.type == contextMenuTriggeringEventType) {
         sendContextMenuEvent(event);
         return true;
     }
 #endif // !OS(MACOSX)
@@ skipping 3163 matching lines @@
     //    the initial viewport width.
     // 2. The author has disabled viewport zoom.
 
     const PageScaleConstraints& constraints = m_pageScaleConstraintsSet.pageDefinedConstraints();
 
     return fixedLayoutSize().width == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 } // namespace WebKit