Use net's response header parser for parsing multipart headers.

net/http/http_util.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 NET_HTTP_HTTP_UTIL_H_
 #define NET_HTTP_HTTP_UTIL_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 129 matching lines @@
 
   // Returns the start of the status line, or -1 if no status line was found.
   // This allows for 4 bytes of junk to precede the status line (which is what
   // mozilla does too).
   static int LocateStartOfStatusLine(const char* buf, int buf_len);
 
   // Returns index beyond the end-of-headers marker or -1 if not found.  RFC
   // 2616 defines the end-of-headers marker as a double CRLF; however, some
   // servers only send back LFs (e.g., Unix-based CGI scripts written using the
   // ASIS Apache module).  This function therefore accepts the pattern LF[CR]LF
-  // as end-of-headers (just like Mozilla).
+  // as end-of-headers (just like Mozilla). The first line of |buf| is
+  // considered the status line, even if empty.
   // The parameter |i| is the offset within |buf| to begin searching from.
   static int LocateEndOfHeaders(const char* buf, int buf_len, int i = 0);
 
+  // Same as |LocateEndOfHeaders|, but does not expect a status line, so can be
+  // used on multi-part responses or HTTP/1.x trailers.  As a result, if |buf|
+  // starts with a single [CR]LF,  it is considered an empty header list, as
+  // opposed to an empty status line above a header list.
+  static int LocateEndOfAdditionalHeaders(const char* buf,
+                                          int buf_len,
+                                          int i = 0);
+
   // Assemble "raw headers" in the format required by HttpResponseHeaders.
   // This involves normalizing line terminators, converting [CR]LF to \0 and
   // handling HTTP line continuations (i.e., lines starting with LWS are
   // continuations of the previous line).  |buf_len| indicates the position of
   // the end-of-headers marker as defined by LocateEndOfHeaders.
   // If a \0 appears within the headers themselves, it will be stripped. This
   // is a workaround to avoid later code from incorrectly interpreting it as
   // a line terminator.
   //
   // TODO(eroman): we should use \n as the canonical line separator rather than
@@ skipping 199 matching lines @@
     // into the original's unquoted_value_ member.
     std::string unquoted_value_;
 
     bool value_is_quoted_;
   };
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_UTIL_H_