macos: only invalidate tiles when size changes

If the size changes, we need to relayout the tiles. Otherwise we can keep
using what we had before. Generally, that shouldn't happen, but the
previous check was failing in a number of ways.

gdk/macos/GdkMacosLayer.c

@@ -317,13 +317,14 @@ fromCGRect (const CGRect rect)
 
 -(void)setFrame:(NSRect)frame
 {
-  if (CGRectEqualToRect (frame, self.frame))
-    return;
-
-  self->_layoutInvalid = TRUE;
+  if (frame.size.width != self.bounds.size.width ||
+      frame.size.height != self.bounds.size.height)
+    {
+      self->_layoutInvalid = TRUE;
+      [self setNeedsLayout];
+    }
 
   [super setFrame:frame];
-  [self setNeedsLayout];
 }
 
 -(void)setOpaqueRegion:(const cairo_region_t *)opaqueRegion