Bug 1204824. Make Matrix4x4::PreScale scale all values in the first three rows. r=bas

gfx/2d/Matrix.h

@@ -698,12 +698,15 @@ public:
     _11 *= aX;
     _12 *= aX;
     _13 *= aX;
+    _14 *= aX;
     _21 *= aY;
     _22 *= aY;
     _23 *= aY;
+    _24 *= aY;
     _31 *= aZ;
     _32 *= aZ;
     _33 *= aZ;
+    _34 *= aZ;
 
     return *this;
   }