Bug 880255. Add an implicit conversion from nsIntSize to IntSize. r=bgirard

--HG--
extra : rebase_source : ac59852b1bf458d181ab8223bc3255ebc0052620

gfx/src/nsSize.h

@@ -8,6 +8,7 @@
 
 #include "nsCoord.h"
 #include "mozilla/gfx/BaseSize.h"
+#include "mozilla/gfx/Point.h"
 
 // Maximum allowable size
 #define NS_MAXSIZE nscoord_MAX
@@ -35,6 +36,7 @@ struct nsIntSize : public mozilla::gfx::BaseSize<int32_t, nsIntSize> {
   nsIntSize(int32_t aWidth, int32_t aHeight) : Super(aWidth, aHeight) {}
 
   inline nsSize ToAppUnits(nscoord aAppUnitsPerPixel) const;
+  operator mozilla::gfx::IntSize() const { return mozilla::gfx::IntSize(width, height); };
 };
 
 inline nsIntSize