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

libcurl_http_fetcher.h

Index: libcurl_http_fetcher.h
diff --git a/libcurl_http_fetcher.h b/libcurl_http_fetcher.h
index 3a50bda46e7ae2ce365f3661f926bc2cb4f2200f..b3ba518d5f6e865b447f5a08f7361e8f74844527 100644
--- a/libcurl_http_fetcher.h
+++ b/libcurl_http_fetcher.h
@@ -48,8 +48,8 @@ class LibcurlHttpFetcher : public HttpFetcher {
   // 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).
@@ -136,6 +136,11 @@ class LibcurlHttpFetcher : public HttpFetcher {
   // 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;