Add support for GYP_DEFINES aura_wm=1 which also defines views_compositor=1.

This build flag will control which set of native types views builds with on various platforms.

Also fixes mouse event handling in the demo app so that the window can be moved.

http://crbug.com/84070
TEST=none
Review URL: http://codereview.chromium.org/7717015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@98086 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/aura/desktop_host_win.cc b/aura/desktop_host_win.cc
index e581b7d..f235b6e 100644
--- a/aura/desktop_host_win.cc
+++ b/aura/desktop_host_win.cc
@@ -57,7 +57,11 @@
                                      LPARAM l_param) {
   MSG msg = { hwnd(), message, w_param, l_param, 0,
               { GET_X_LPARAM(l_param), GET_Y_LPARAM(l_param) } };
-  SetMsgHandled(desktop_->OnMouseEvent(MouseEvent(msg)));
+  MouseEvent event(msg);
+  bool handled = false;
+  if (!(event.flags() & ui::EF_IS_NON_CLIENT))
+    handled = desktop_->OnMouseEvent(event);
+  SetMsgHandled(handled);
   return 0;
 }