AU: Fix potential issues with premature destruction of HTTP fetchers.

libcurl_http_fetcher.h

 // Copyright (c) 2009 The Chromium OS 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 CHROMEOS_PLATFORM_UPDATE_ENGINE_LIBCURL_HTTP_FETCHER_H__
 #define CHROMEOS_PLATFORM_UPDATE_ENGINE_LIBCURL_HTTP_FETCHER_H__
 
 #include <map>
 #include <string>
 #include <curl/curl.h>
@@ skipping 30 matching lines @@
         terminate_requested_(false) {}
 
   // Cleans up all internal state. Does not notify delegate
   ~LibcurlHttpFetcher();
 
   void SetOffset(off_t offset) { bytes_downloaded_ = offset; }
 
   // Begins the transfer if it hasn't already begun.
   virtual void BeginTransfer(const std::string& url);
 
-  // If the transfer is in progress, aborts the transfer early.
-  // The transfer cannot be resumed.
+  // If the transfer is in progress, aborts the transfer early. The transfer
+  // cannot be resumed.
   virtual void TerminateTransfer();
 
   // Suspend the transfer by calling curl_easy_pause(CURLPAUSE_ALL).
   virtual void Pause();
 
   // Resume the transfer by calling curl_easy_pause(CURLPAUSE_CONT).
   virtual void Unpause();
 
   // Libcurl sometimes asks to be called back after some time while
   // leaving that time unspecified. In that case, we pick a reasonable
@@ skipping 66 matching lines @@
   static size_t StaticLibcurlWrite(void *ptr, size_t size,
                                    size_t nmemb, void *stream) {
     return reinterpret_cast<LibcurlHttpFetcher*>(stream)->
         LibcurlWrite(ptr, size, nmemb);
   }
 
   // Cleans up the following if they are non-null:
   // curl(m) handles, io_channels_, timeout_source_.
   void CleanUp();
 
+  // Force terminate the transfer. This will invoke the delegate's (if any)
+  // TransferTerminated callback so, after returning, this fetcher instance may
+  // be destroyed.
+  void ForceTransferTermination();
+
   // Returns whether or not the current network connection is considered
   // expensive.
   bool ConnectionIsExpensive() const;
 
   // Returns whether or not the current build is official.
   bool IsOfficialBuild() const;
 
   // Handles for the libcurl library
   CURLM *curl_multi_handle_;
   CURL *curl_handle_;
@@ skipping 48 matching lines @@
   // We can't clean everything up while we're in a write callback, so
   // if we get a terminate request, queue it until we can handle it.
   bool terminate_requested_;
 
   DISALLOW_COPY_AND_ASSIGN(LibcurlHttpFetcher);
 };
 
 }  // namespace chromeos_update_engine
 
 #endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_LIBCURL_HTTP_FETCHER_H__