Add static method WebApkIconHasher::DownloadAndComputeMurmur2Hash

chrome/browser/android/webapk/webapk_icon_hasher.h

 // 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.
 
 #ifndef CHROME_BROWSER_ANDROID_WEBAPK_WEBAPK_ICON_HASHER_H_
 #define CHROME_BROWSER_ANDROID_WEBAPK_WEBAPK_ICON_HASHER_H_
 
 #include <memory>
 #include <string>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/timer/timer.h"
 #include "net/url_request/url_fetcher_delegate.h"
 #include "url/gurl.h"
 
 namespace net {
 class URLFetcher;
 class URLRequestContextGetter;
 }
 
 // Downloads an icon and takes a Murmur2 hash of the downloaded image.
 class WebApkIconHasher : public net::URLFetcherDelegate {
  public:
   using Murmur2HashCallback =
       base::Callback<void(const std::string& /* icon_murmur2_hash */)>;
 
+  // Creates a self-owned WebApkIconHasher instance. The instance downloads
+  // |icon_url| and calls |callback| with the Murmur2 hash of the downloaded
+  // image. The hash is taken over the raw image bytes (no image
+  // encoding/decoding beforehand). |callback| is called with an empty string if
+  // the image cannot not be downloaded in time (e.g. 404 HTTP error code).
+  static void DownloadAndComputeMurmur2Hash(
+      net::URLRequestContextGetter* request_context_getter,
+      const GURL& icon_url,
+      const Murmur2HashCallback& callback);
+
+ private:
   WebApkIconHasher(
       net::URLRequestContextGetter* request_context_getter,
       const GURL& icon_url,
       const Murmur2HashCallback& callback);
   ~WebApkIconHasher() override;
 
-  // Downloads |icon_url_|. Calls |callback_| with the Murmur2 hash of the
-  // downloaded image. The hash is taken over the raw image bytes (no image
-  // encoding/decoding beforehand). |callback_| is called with an empty string
-  // if the image cannot not be downloaded in time (e.g. 404 HTTP error code).
-  void DownloadAndComputeMurmur2Hash();
-
- private:
   // net::URLFetcherDelegate:
   void OnURLFetchComplete(const net::URLFetcher* source) override;
 
   // Called if downloading the icon takes too long.
   void OnDownloadTimedOut();
 
-  // For retrieving URLRequestContext. Owned by the caller of this class.
-  net::URLRequestContextGetter* url_request_context_getter_;
-
-  // The icon URL.
-  GURL icon_url_;
+  // Calls |callback_| with |icon_murmur2_hash|. Also deletes the instance.
+  void RunCallback(const std::string& icon_murmur2_hash);
 
   // Called with the image hash.
   Murmur2HashCallback callback_;
 
   std::unique_ptr<net::URLFetcher> url_fetcher_;
 
   // Fails WebApkIconHasher if the download takes too long.
   base::OneShotTimer download_timeout_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(WebApkIconHasher);
 };
 
 #endif  // CHROME_BROWSER_ANDROID_WEBAPK_WEBAPK_ICON_HASHER_H_