Disable the Context Menu in the tab-modal signin dialog.

chrome/browser/ui/signin_view_controller_delegate.cc

 // Copyright 2016 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.
 
 #include "chrome/browser/ui/signin_view_controller_delegate.h"
 
 #include "base/bind.h"
 #include "base/values.h"
 #include "chrome/browser/ui/signin_view_controller.h"
 #include "chrome/browser/ui/webui/signin/get_auth_frame.h"
@@ skipping 16 matching lines @@
   web_contents_->SetDelegate(this);
 }
 
 SigninViewControllerDelegate::~SigninViewControllerDelegate() {}
 
 void SigninViewControllerDelegate::CloseModalSignin() {
   ResetSigninViewControllerDelegate();
   PerformClose();
 }
 
+void SigninViewControllerDelegate::PerformNavigation() {
+  if (CanGoBack(web_contents_)) {
+    auto auth_web_contents = GetAuthFrameWebContents(web_contents_);
+    auth_web_contents->GetController().GoBack();
+  } else {
+    CloseModalSignin();
+  }
+}
+
+bool SigninViewControllerDelegate::HandleContextMenu(
+    const content::ContextMenuParams& params) {
+  // Discard the context menu
+  return true;
+}
+
 void SigninViewControllerDelegate::ResetSigninViewControllerDelegate() {
   if (signin_view_controller_) {
     signin_view_controller_->ResetModalSigninDelegate();
     signin_view_controller_ = nullptr;
   }
 }
 
-bool SigninViewControllerDelegate::CanGoBack(
-    content::WebContents* web_ui_web_contents) const {
-  auto auth_web_contents = GetAuthFrameWebContents(web_ui_web_contents);
-  return auth_web_contents && auth_web_contents->GetController().CanGoBack();
-}
-
 // content::WebContentsDelegate
 void SigninViewControllerDelegate::LoadingStateChanged(
     content::WebContents* source,
     bool to_different_document) {
   if (CanGoBack(source))
     source->GetWebUI()->CallJavascriptFunctionUnsafe(
         "inline.login.showBackButton");
   else
     source->GetWebUI()->CallJavascriptFunctionUnsafe(
         "inline.login.showCloseButton");
 }
 
-void SigninViewControllerDelegate::PerformNavigation() {
-  if (CanGoBack(web_contents_)) {
-    auto auth_web_contents = GetAuthFrameWebContents(web_contents_);
-    auth_web_contents->GetController().GoBack();
-  } else {
-    CloseModalSignin();
-  }
+bool SigninViewControllerDelegate::CanGoBack(
+    content::WebContents* web_ui_web_contents) const {
+  auto auth_web_contents = GetAuthFrameWebContents(web_ui_web_contents);
+  return auth_web_contents && auth_web_contents->GetController().CanGoBack();
 }