[Mac] Allow fullscreen transitions while constrained windows are open.

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 f261abb8e37d01e1ccac1185de6cc65cde825eef..65c4c4a81ae220cecc5a7dd64dc08da367c66977 100644
--- a/chrome/browser/ui/cocoa/browser_window_controller_private.mm
+++ b/chrome/browser/ui/cocoa/browser_window_controller_private.mm
@@ -277,6 +277,20 @@ willPositionSheet:(NSWindow*)sheet
   // Normally, we don't need to tell the toolbar whether or not to show the
   // divider, but things break down during animation.
   [toolbarController_ setDividerOpacity:[self toolbarDividerOpacity]];
+
+  // Update the position of the active constrained window sheet.  We force this
+  // here because the |sheetParentView| may not have been resized (e.g., to
+  // prevent jank during a fullscreen mode transition), but constrained window
+  // sheets also compute their position based on the bookmark bar and toolbar.
+  content::WebContents* const activeWebContents =
+      browser_->tab_strip_model()->GetActiveWebContents();
+  NSView* const sheetParentView = activeWebContents ?
+      GetSheetParentViewForWebContents(activeWebContents) : nil;
+  if (sheetParentView) {
+    [[NSNotificationCenter defaultCenter]
+      postNotificationName:NSViewFrameDidChangeNotification
+                    object:sheetParentView];
+  }
 }
 
 - (CGFloat)floatingBarHeight {