Add the ability to override WebContentsBindingSet binders for testing

content/public/test/web_contents_binding_set_test_binder.h

Index: content/public/test/web_contents_binding_set_test_binder.h
diff --git a/content/public/test/web_contents_binding_set_test_binder.h b/content/public/test/web_contents_binding_set_test_binder.h
new file mode 100644
index 0000000000000000000000000000000000000000..755bbdae67890e39478a4de79b43f73a4a523db0
--- /dev/null
+++ b/content/public/test/web_contents_binding_set_test_binder.h
@@ -0,0 +1,34 @@
+// Copyright 2017 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 "mojo/public/cpp/bindings/associated_interface_request.h"
+
+namespace content {
+
+// Helper class which test code can use with
+// WebContentsImpl::OverrideBinderForTesting() in order to override
+// WebContentsBindingSet interface binding behavior in tests.
+template <typename Interface>
+class WebContentsBindingSetTestBinder : public WebContentsBindingSet::Binder {
+ public:
+  ~WebContentsBindingSetTestBinder() override {}
+
+  // Call for every new incoming interface request for a frame.
+  virtual void BindRequest(
+      RenderFrameHost* render_frame_host,
+      mojo::AssociatedInterfaceRequest<Interface> request) = 0;
+
+ private:
+  // Binder:
+  void OnRequestForFrame(RenderFrameHost* render_frame_host,
+                         mojo::ScopedInterfaceEndpointHandle handle) override {
+    mojo::AssociatedInterfaceRequest<Interface> request;
+    request.Bind(std::move(handle));
+    BindRequest(render_frame_host, std::move(request));
+  }
+};
+
+}  // namespace content