Offline Pages: Use 'binary encoding' to create MHTML, instead of base64.

content/common/frame_messages.h

 // Copyright 2013 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.
 
 // IPC messages for interacting with frames.
 // Multiply-included message file, hence no include guard.
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 478 matching lines @@
   // Job id - used to match responses to requests.
   IPC_STRUCT_MEMBER(int, job_id)
 
   // Destination file handle.
   IPC_STRUCT_MEMBER(IPC::PlatformFileForTransit, destination_file)
 
   // MHTML boundary marker / MIME multipart boundary maker.  The same
   // |mhtml_boundary_marker| should be used for serialization of each frame.
   IPC_STRUCT_MEMBER(std::string, mhtml_boundary_marker)
 
+  // Whether to use binary encoding while serializing.  Binary encoding is not
+  // supported outside of Chrome, so this should not be used if the MHTML is
+  // intended for sharing.
+  IPC_STRUCT_MEMBER(bool, mhtml_binary_encoding)
+
   // Frame to content-id map.
   // Keys are routing ids of either RenderFrames or RenderFrameProxies.
   // Values are MHTML content-ids - see WebFrameSerializer::generateMHTMLParts.
   IPC_STRUCT_MEMBER(FrameMsg_SerializeAsMHTML_FrameRoutingIdToContentIdMap,
                     frame_routing_id_to_content_id)
 
   // |digests_of_uris_to_skip| contains digests of uris of MHTML parts that
   // should be skipped.  This helps deduplicate mhtml parts across frames.
   // SECURITY NOTE: Sha256 digests (rather than uris) are used to prevent
   // disclosing uris to other renderer processes;  the digests should be
@@ skipping 932 matching lines @@
 IPC_MESSAGE_ROUTED3(FrameHostMsg_FindMatchRects_Reply,
                     int /* version */,
                     std::vector<gfx::RectF> /* rects */,
                     gfx::RectF /* active_rect */)
 #endif
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent FrameMsg, then ifdefs for platform specific FrameMsg, then
 // platform independent FrameHostMsg, then ifdefs for platform specific
 // FrameHostMsg.