Add Digital Asset Links verification for postMessage API

chrome/browser/android/digital_asset_links/digital_asset_links_handler.h

+// Copyright (c) 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.
+
+#ifndef CHROME_BROWSER_ANDROID_DIGITAL_ASSET_LINKS_DIGITAL_ASSET_LINKS_HANDLER_H_
+#define CHROME_BROWSER_ANDROID_DIGITAL_ASSET_LINKS_DIGITAL_ASSET_LINKS_HANDLER_H_
+
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_fetcher_delegate.h"
+#include "net/url_request/url_request_context_getter.h"
+
+namespace base {
+class DictionaryValue;
+}
+
+namespace digital_asset_links {
+
+extern const char kDigitalAssetLinksCheckResponseKeyLinked[];
+
+typedef base::Callback<void(std::unique_ptr<base::DictionaryValue>)>

[nyquist, 2017/04/19 06:35:57]

Nit: On a failure what will the parameter to this callback be? (nullptr)
What about on success?
What are the expected fields in the dictionary?

[Yusuf, 2017/04/26 00:51:36]

Documented the failure case. On success depends on what API they used. Check and
List returns different things. Added a top level reference to APIs.

[nyquist, 2017/04/27 04:38:25]

Awesome with the referral to the REST API. Very helpful!

+    RelationshipCheckResultCallback;
+
+class DigitalAssetLinksHandler : public net::URLFetcherDelegate {

[nyquist, 2017/04/19 06:35:57]

Nit: What is this class used for? What is the lifetime for this class? On which
thread should it be constructed and destroyed on?

Also, is there some spec you can refer to, either here or in the implementation?

[Yusuf, 2017/04/26 00:51:36]

Done.

+ public:
+  DigitalAssetLinksHandler(

[nyquist, 2017/04/19 06:35:57]

Nit: Single argument constructors should be marked as explicit.

[Yusuf, 2017/04/26 00:51:36]

Done.

+      const scoped_refptr<net::URLRequestContextGetter>& request_context);
+  ~DigitalAssetLinksHandler() override;
+
+  bool CheckDigitalAssetLinkRelationship(

[nyquist, 2017/04/19 06:35:57]

Nit: Could you explain what this method does?
What does this return? From which thread can it be called?
What are the guarantees for invoking the callback? Will it be re-entrant, or
will the result always be posted?

What are the different params? Like what's |relationship|?
What type of value is |fingerprint|?

[Yusuf, 2017/04/26 00:51:36]

Done.

+      RelationshipCheckResultCallback listener,
+      const std::string& web_domain,
+      const std::string& package_name,
+      const std::string& fingerprint,
+      const std::string& relationship);
+
+ private:
+  // net::URLFetcherDelegate:
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+  scoped_refptr<net::URLRequestContextGetter> request_context_;
+
+  std::unique_ptr<net::URLFetcher> url_fetcher_;
+
+  // The callback for receiving a URLFetcher result.
+  RelationshipCheckResultCallback callback_;

[nyquist, 2017/04/19 06:35:57]

So, this is a little bit confusing. It's passed in to the constructor, and
stored for re-use, but it's still called a Callback.
I think it'd be super helpful to clarify how this class is supposed to be used,
i.e. is it a one-off or something that you can continuously call?

[Yusuf, 2017/04/26 00:51:36]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(DigitalAssetLinksHandler);
+};
+
+}  // namespace digital_asset_links
+
+#endif  // CHROME_BROWSER_ANDROID_DIGITAL_ASSET_LINKS_DIGITAL_ASSET_LINKS_HANDLER_H_