Mac: Remove dead code

|childWindowsDidChange| was removed from the delegate, so these methods
are now noops.

Change-Id: I5becdd5797c0adc14a9c2f53d0f78d5ce684ceea
Reviewed-on: https://chromium-review.googlesource.com/1040946Reviewed-by: Sidney San Martín <sdy@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555805}

chrome/browser/ui/cocoa/framed_browser_window.mm

@@ -27,10 +27,6 @@
 #import "ui/base/cocoa/nsview_additions.h"
 #import "ui/base/cocoa/touch_bar_forward_declarations.h"
 
-@interface FramedBrowserWindow ()
-- (void)childWindowsDidChange;
-@end
-
 @implementation FramedBrowserWindow
 
 + (CGFloat)browserFrameViewPaintHeight {
@@ -212,21 +208,4 @@
     return [NSColor windowFrameTextColor];
 }
 
-- (void)addChildWindow:(NSWindow*)childWindow
-               ordered:(NSWindowOrderingMode)orderingMode {
-  [super addChildWindow:childWindow ordered:orderingMode];
-  [self childWindowsDidChange];
-}
-
-- (void)removeChildWindow:(NSWindow*)childWindow {
-  [super removeChildWindow:childWindow];
-  [self childWindowsDidChange];
-}
-
-- (void)childWindowsDidChange {
-  id delegate = [self delegate];
-  if ([delegate respondsToSelector:@selector(childWindowsDidChange)])
-    [delegate childWindowsDidChange];
-}
-
 @end