Upstream most of the iOS WebUI support in ios/web/

ios/web/webui/url_fetcher_block_adapter.h

Index: ios/web/webui/url_fetcher_block_adapter.h
diff --git a/ios/web/webui/url_fetcher_block_adapter.h b/ios/web/webui/url_fetcher_block_adapter.h
new file mode 100644
index 0000000000000000000000000000000000000000..1e2f055d9a7b78d6bf79b3e40e49591c8f9fb9e8
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+// Copyright 2015 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 IOS_WEB_WEBUI_URL_FETCHER_BLOCK_ADAPTER_H_
+#define IOS_WEB_WEBUI_URL_FETCHER_BLOCK_ADAPTER_H_
+
+#import <Foundation/Foundation.h>
+
+#include "base/mac/scoped_block.h"
+#include "base/memory/scoped_ptr.h"
+#include "net/url_request/url_fetcher_delegate.h"
+#include "url/gurl.h"
+
+namespace net {
+class URLFetcher;
+class URLRequestContextGetter;
+}  // namespace net
+
+namespace web {
+
+// Class for use of URLFetcher from Objective-C with a completion handler block.
+class URLFetcherBlockAdapter;
+// Block type for URLFetcherBlockAdapter callbacks.
+typedef void (^URLFetcherBlockAdapterCompletion)(NSData*,
+                                                 URLFetcherBlockAdapter*);
+
+// Class to manage retrieval of WebUI resources.
+class URLFetcherBlockAdapter : public net::URLFetcherDelegate {
+ public:
+  // Create URLFetcherBlockAdapter for resource at |url| with |request_context|.
+  // |completion_handler| is called with results of the fetch.
+  URLFetcherBlockAdapter(
+      const GURL& url,
+      net::URLRequestContextGetter* request_context,
+      web::URLFetcherBlockAdapterCompletion completion_handler);
+  ~URLFetcherBlockAdapter() override;
+  // Start the fetch.
+  void Start();
+
+ protected:
+  // net::URLFetcherDelegate implementation.
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+ private:
+  // The URL to fetch.
+  const GURL url_;
+  // The request context.
+  net::URLRequestContextGetter* request_context_;
+  // Callback for resource load.
+  base::mac::ScopedBlock<web::URLFetcherBlockAdapterCompletion>
+      completion_handler_;
+  // URLFetcher for retrieving data from net stack.
+  scoped_ptr<net::URLFetcher> fetcher_;
+};
+
+}  // namespace web
+
+#endif  // IOS_WEB_WEBUI_URL_FETCHER_BLOCK_ADAPTER_H_