Mac: Fix a recently introduced layering bug.

chrome/browser/ui/cocoa/browser_window_controller_private.mm

Index: chrome/browser/ui/cocoa/browser_window_controller_private.mm
diff --git a/chrome/browser/ui/cocoa/browser_window_controller_private.mm b/chrome/browser/ui/cocoa/browser_window_controller_private.mm
index c4f5c6f70853ecec90e2be1844a7cabfecded22a..9ae19ccc8299a14346d820e15050d1cc37a2944a 100644
--- a/chrome/browser/ui/cocoa/browser_window_controller_private.mm
+++ b/chrome/browser/ui/cocoa/browser_window_controller_private.mm
@@ -677,6 +677,7 @@ willPositionSheet:(NSWindow*)sheet
       // Leaving wantsLayer on for the duration of presentation mode causes
       // performance issues when the dropdown is animated in/out.  It also does
       // not seem to be required for the exit animation.
+      windowViewWantsLayer_ = [[[self window] cr_windowView] wantsLayer];
       [[[self window] cr_windowView] setWantsLayer:YES];
     }
     NSView* contentView = [[self window] contentView];
@@ -914,7 +915,7 @@ willPositionSheet:(NSWindow*)sheet
 
   [self showFullscreenExitBubbleIfNecessary];
   browser_->WindowFullscreenStateChanged();
-  [[[self window] cr_windowView] setWantsLayer:NO];
+  [[[self window] cr_windowView] setWantsLayer:windowViewWantsLayer_];
   [self updateRoundedBottomCorners];
 }