[Downloads] Always call DM::StartDownload() for explicit downloads.

content/browser/download/download_request_core.h

 // Copyright (c) 2012 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 CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_REQUEST_CORE_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_REQUEST_CORE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "content/browser/loader/resource_handler.h"
 #include "content/public/browser/download_interrupt_reasons.h"
 #include "content/public/browser/download_save_info.h"
 #include "content/public/browser/download_url_parameters.h"
 
 namespace net {
+class HttpResponseHeaders;
 class URLRequest;
+class URLRequestStatus;
 }  // namespace net
 
 namespace content {
 class DownloadManagerImpl;
 class ByteStreamReader;
 class ByteStreamWriter;
 class PowerSaveBlocker;
 struct DownloadCreateInfo;
 
 // This class encapsulates the core logic for reading data from a URLRequest and
 // writing it into a ByteStream. It's common to both DownloadResourceHandler and
 // UrlDownloader.
 //
 // Created, lives on and dies on the IO thread.
 class CONTENT_EXPORT DownloadRequestCore
     : public base::SupportsWeakPtr<DownloadRequestCore> {
  public:
-  // Size of the buffer used between the DownloadRequestCore and the
-  // downstream receiver of its output.
-  static const int kDownloadByteStreamSize;
+  class Delegate {
+   public:
+    virtual void OnReadyToRead() = 0;
+    virtual void OnStart(
+        scoped_ptr<DownloadCreateInfo> download_create_info,
+        scoped_ptr<ByteStreamReader> stream_reader,
+        const DownloadUrlParameters::OnStartedCallback& callback) = 0;
+  };
 
-  // |request| *must* outlive the DownloadRequestCore. |save_info| must be
-  // valid.
-  //
-  // Invokes |on_ready_to_read_callback| if a previous call to OnReadCompleted()
-  // resulted in |defer| being set to true, and DownloadRequestCore is now ready
-  // to commence reading.
-  DownloadRequestCore(net::URLRequest* request,
-                      scoped_ptr<DownloadSaveInfo> save_info,
-                      const base::Closure& on_ready_to_read_callback);
+  // All parameters are required. |request| and |delegate| must outlive
+  // DownloadRequestCore.
+  DownloadRequestCore(net::URLRequest* request, Delegate* delegate);
   ~DownloadRequestCore();
 
   // Should be called when the URLRequest::Delegate receives OnResponseStarted.
-  // Constructs a DownloadCreateInfo and a ByteStreamReader that should be
-  // passed into DownloadManagerImpl::StartDownload().
-  //
-  // Only populates the response derived fields of DownloadCreateInfo, with the
-  // exception of |save_info|.
-  void OnResponseStarted(scoped_ptr<DownloadCreateInfo>* info,
-                         scoped_ptr<ByteStreamReader>* stream_reader);
+  // Invokes Delegate::OnStart() with download start parameters.

[Randy Smith (Not in Mondays), 2016/02/12 18:58:11]

nit: comment use of parameter.

[asanka, 2016/02/12 20:52:29]

Done.

+  bool OnResponseStarted(const std::string& override_mime_type);
 
   // Starts a read cycle. Creates a new IOBuffer which can be passed into
   // URLRequest::Read(). Call OnReadCompleted() when the Read operation
   // completes.
   bool OnWillRead(scoped_refptr<net::IOBuffer>* buf,
                   int* buf_size,
                   int min_size);
 
   // Should be called when the Read() operation completes. |defer| will be set
   // to true if reading is to be suspended. In the latter case, once more data
   // can be read, invokes the |on_ready_to_read_callback|.
   bool OnReadCompleted(int bytes_read, bool* defer);
 
-  // Called to signal that the response is complete. If the return value is
-  // something other than DOWNLOAD_INTERRUPT_REASON_NONE, then the download
-  // should be considered interrupted.
+  // Called to signal that the response is complete.
   //
   // It is expected that once this method is invoked, the DownloadRequestCore
   // object will be destroyed in short order without invoking any other methods
   // other than the destructor.
-  DownloadInterruptReason OnResponseCompleted(
-      const net::URLRequestStatus& status);
+  void OnResponseCompleted(const net::URLRequestStatus& status);
 
   // Called if the request should suspend reading. A subsequent
   // OnReadCompleted() will result in |defer| being set to true.
   //
   // Each PauseRequest() must be balanced with a call to ResumeRequest().
   void PauseRequest();
 
   // Balances a call to PauseRequest(). If no more pauses are outstanding and
   // the reader end of the ByteStream is ready to receive more data,
   // DownloadRequestCore will invoke the |on_ready_to_read_callback| to signal
   // to the caller that the read cycles should commence.
   void ResumeRequest();
 
   std::string DebugString() const;
 
+  static scoped_ptr<net::URLRequest> CreateRequestOnIOThread(
+      uint32_t download_id,
+      DownloadUrlParameters* params);
+
+  // Size of the buffer used between the DownloadRequestCore and the
+  // downstream receiver of its output.
+  static const int kDownloadByteStreamSize;
+
  protected:
   net::URLRequest* request() const { return request_; }
 
  private:
-  base::Closure on_ready_to_read_callback_;
+  static DownloadInterruptReason HandleRequestStatus(
+      const net::URLRequestStatus& status);
+
+  static DownloadInterruptReason HandleSuccessfulServerResponse(
+      const net::HttpResponseHeaders& http_headers,
+      DownloadSaveInfo* save_info);
+
+  scoped_ptr<DownloadCreateInfo> CreateDownloadCreateInfo(
+      DownloadInterruptReason result,
+      const std::string& override_mime_type);
+
+  Delegate* delegate_;
   net::URLRequest* request_;
+
+  // "Passthrough" fields. These are only kept here so that they can be used to
+  // populate the DownloadCreateInfo when the time comes.
   scoped_ptr<DownloadSaveInfo> save_info_;
+  uint32_t download_id_;
+  DownloadUrlParameters::OnStartedCallback on_started_callback_;
 
   // Data flow
   scoped_refptr<net::IOBuffer> read_buffer_;    // From URLRequest.
   scoped_ptr<ByteStreamWriter> stream_writer_;  // To rest of system.
 
   // Keeps the system from sleeping while this is alive. If the
   // system enters power saving mode while a request is alive, it can cause the
   // request to fail and the associated download will be interrupted.
   scoped_ptr<PowerSaveBlocker> power_save_blocker_;
 
   // The following are used to collect stats.
   base::TimeTicks download_start_time_;
   base::TimeTicks last_read_time_;
   base::TimeTicks last_stream_pause_time_;
   base::TimeDelta total_pause_time_;
   size_t last_buffer_size_;
   int64_t bytes_read_;
 
   int pause_count_;
   bool was_deferred_;
+  bool is_resumption_request_;
+  bool started_;
+
+  // When DownloadRequestCore initiates an abort (by blocking a redirect, for
+  // example) it expects to eventually receive a OnResponseCompleted() with a
+  // status indicating that the request was aborted. When this happens, the
+  // interrupt reason in |abort_reason_| will be used instead of USER_CANCELED
+  // which is vague.
+  DownloadInterruptReason abort_reason_;
 
   // Each successful OnWillRead will yield a buffer of this size.
   static const int kReadBufSize = 32768;   // bytes
 
   DISALLOW_COPY_AND_ASSIGN(DownloadRequestCore);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_REQUEST_CORE_H_