MacViews: Unify web contents modal dialog types

chrome/browser/ui/cocoa/ssl_client_certificate_selector_cocoa.mm

Index: chrome/browser/ui/cocoa/ssl_client_certificate_selector_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/ssl_client_certificate_selector_cocoa.mm b/chrome/browser/ui/cocoa/ssl_client_certificate_selector_cocoa.mm
index 9d471b923de6fe2903f327656efcdfd7df25dc2e..a8d7912f5204808919e499b1910929f09ab09571 100644
--- a/chrome/browser/ui/cocoa/ssl_client_certificate_selector_cocoa.mm
+++ b/chrome/browser/ui/cocoa/ssl_client_certificate_selector_cocoa.mm
@@ -227,6 +227,10 @@ void ShowSSLClientCertificateSelector(
   // NOOP
 }
 
+- (NSWindow*)sheetWindow {
+  return panel_;
+}
+
 - (void)onConstrainedWindowClosed {
   observer_->StopObserving();
   panel_.reset();