Bug 1445444: Properly initialize plugin window drawing type on Windows r=jimm

Sets the default plugin window type to windowed on Windows.  Most of the time, plugins use async drawing so this will be overwritten but it should be properly initialized for cases where we do not switch to async.

dom/plugins/base/nsPluginNativeWindowWin.cpp

@@ -475,6 +475,7 @@ nsPluginNativeWindowWin::nsPluginNativeWindowWin() : nsPluginNativeWindow()
   y = 0;
   width = 0;
   height = 0;
+  type = NPWindowTypeWindow;
 
   mPrevWinProc = nullptr;
   mPluginWinProc = nullptr;