Take Murmur2 hash of untransformed icon when creating WebAPK part 1

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/time/time.h"
+#include "net/url_request/url_fetcher_delegate.h"
+
+namespace net {
+class URLFetcher;
+class URLRequestContextGetter;
+}
+
+class GURL;
+
+// 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 */)>;
+
+  WebApkIconHasher();
+  ~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 (e.g. 404 HTTP error code).
+  void DownloadAndComputeMurmur2Hash(
+      net::URLRequestContextGetter* request_context_getter,
+      const GURL& icon_url,
+      const Murmur2HashCallback& callback);
+
+ private:
+  // net::URLFetcherDelegate:
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+  // Fetches the image.
+  std::unique_ptr<net::URLFetcher> url_fetcher_;
+
+  // Called with the image hash.
+  Murmur2HashCallback callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(WebApkIconHasher);
+};
+
+#endif  // CHROME_BROWSER_ANDROID_WEBAPK_WEBAPK_ICON_HASHER_H_