Add the ability to override WebContentsBindingSet binders for testing

content/public/browser/web_contents_binding_set.h

Index: content/public/browser/web_contents_binding_set.h
diff --git a/content/public/browser/web_contents_binding_set.h b/content/public/browser/web_contents_binding_set.h
index 1d3290f08da84962f30407f06d9636dde8efad60..d65fbd8650323ea31d0bc12f6f1a266d76ea320f 100644
--- a/content/public/browser/web_contents_binding_set.h
+++ b/content/public/browser/web_contents_binding_set.h
@@ -25,7 +25,7 @@ class WebContentsImpl;
 // Base class for something which owns a mojo::AssociatedBindingSet on behalf
 // of a WebContents. See WebContentsFrameBindingSet<T> below.
 class CONTENT_EXPORT WebContentsBindingSet {
- protected:
+ public:
   class CONTENT_EXPORT Binder {
    public:
     virtual ~Binder() {}
@@ -35,6 +35,37 @@ class CONTENT_EXPORT WebContentsBindingSet {
         mojo::ScopedInterfaceEndpointHandle handle);
   };
 
+  // Helper class which test code can use with SetBinderForTesting() in order
+  // to override interface binding behavior in tests. Once this is set on a
+  // WebContentsBindingSet via SetBinderForTesting (see below), it will live
+  // until either it is replaced or the WebContents is destroyed.
+  template <typename Interface>
+  class TestBinder : public Binder {

[jam, 2017/03/20 17:07:32]

can this be moved to content/public/test?

[Ken Rockot(use gerrit already), 2017/03/20 17:50:47]

Done

+   public:
+    ~TestBinder() 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));
+    }
+  };
+
+  template <typename Interface>
+  void SetBinderForTesting(std::unique_ptr<TestBinder<Interface>> binder) {
+    binder_for_testing_ = std::move(binder);
+  }
+
+ protected:
   WebContentsBindingSet(WebContents* web_contents,
                         const std::string& interface_name,
                         std::unique_ptr<Binder> binder);
@@ -49,6 +80,7 @@ class CONTENT_EXPORT WebContentsBindingSet {
 
   const base::Closure remove_callback_;
   std::unique_ptr<Binder> binder_;
+  std::unique_ptr<Binder> binder_for_testing_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentsBindingSet);
 };