[MacViews] Fix behavior of non-resizable windows in fullscreen.

ui/views/cocoa/views_nswindow_delegate.mm

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ui/views/cocoa/views_nswindow_delegate.h"
 
 #include "base/logging.h"
 #import "ui/views/cocoa/bridged_content_view.h"
 #import "ui/views/cocoa/bridged_native_widget.h"
 #include "ui/views/widget/native_widget_mac.h"
@@ skipping 98 matching lines @@
 }
 
 - (void)windowWillExitFullScreen:(NSNotification*)notification {
   parent_->OnFullscreenTransitionStart(false);
 }
 
 - (void)windowDidExitFullScreen:(NSNotification*)notification {
   parent_->OnFullscreenTransitionComplete(false);
 }
 
+// Allow non-resizable windows (without NSResizableWindowMask) to fill the
+// screen in fullscreen mode. This only happens when
+// -[NSWindow toggleFullscreen:] is called since non-resizable windows have no
+// fullscreen button. Without this they would only enter fullscreen at their
+// current size.
+- (NSSize)window:(NSWindow*)window
+    willUseFullScreenContentSize:(NSSize)proposedSize {
+  return proposedSize;
+}
+
 @end