Add the ability to override WebContentsBindingSet binders for testing

content/public/browser/web_contents_binding_set.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 "content/public/browser/web_contents_binding_set.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 
 namespace content {
 
 void WebContentsBindingSet::Binder::OnRequestForFrame(
     RenderFrameHost* render_frame_host,
     mojo::ScopedInterfaceEndpointHandle handle) {
   NOTREACHED();
 }
 
 WebContentsBindingSet::WebContentsBindingSet(WebContents* web_contents,
                                              const std::string& interface_name,
                                              std::unique_ptr<Binder> binder)
-    : remove_callback_(
-          static_cast<WebContentsImpl*>(web_contents)->AddBindingSet(
-              interface_name, this)),
+    : remove_callback_(static_cast<WebContentsImpl*>(web_contents)
+                           ->AddBindingSet(interface_name, this)),
       binder_(std::move(binder)) {}
 
 WebContentsBindingSet::~WebContentsBindingSet() {
   remove_callback_.Run();
 }
 
 void WebContentsBindingSet::CloseAllBindings() {
+  binder_for_testing_.reset();
   binder_.reset();
 }
 
 void WebContentsBindingSet::OnRequestForFrame(
     RenderFrameHost* render_frame_host,
     mojo::ScopedInterfaceEndpointHandle handle) {
+  if (binder_for_testing_) {
+    binder_for_testing_->OnRequestForFrame(render_frame_host,
+                                           std::move(handle));
+    return;
+  }
   DCHECK(binder_);
   binder_->OnRequestForFrame(render_frame_host, std::move(handle));
 }
 
 }  // namespace content