Fix window origin on mac views

Bug: skia:
Change-Id: I25e4e791760bd1d95a2bfac1a1b5d18d9caa78e8
Reviewed-on: https://skia-review.googlesource.com/56581
Reviewed-by: Yuqian Li <liyuqian@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>

src/views/mac/SkNSView.mm

@@ -53,7 +53,7 @@ BOOL fRedrawRequestPending;
 
 - (void)setNSViewSize:(NSSize)size {
     NSWindow* w = [self window];
-    NSRect f;
+    NSRect f = w.frame;
     f.size = size;
     [w setFrame:f display:YES];
 }