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

ui/views/cocoa/views_nswindow_delegate.mm

Index: ui/views/cocoa/views_nswindow_delegate.mm
diff --git a/ui/views/cocoa/views_nswindow_delegate.mm b/ui/views/cocoa/views_nswindow_delegate.mm
index 6a344a38fa330e02742142f85982dc5cdfd6ee76..777348d94d9bc5f04a43e55e6bdf27e725208070 100644
--- a/ui/views/cocoa/views_nswindow_delegate.mm
+++ b/ui/views/cocoa/views_nswindow_delegate.mm
@@ -116,4 +116,14 @@
   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