Add support for multipage distillation.

components/dom_distiller/core/proto/distilled_page.proto

 // 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.
 //
 // Distilled page content.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 package dom_distiller;
 
 message DistilledPageProto {
   // The URLs used to create this page.
   required string url = 1;
 
-  // A title for the distilled page.
-  optional string title = 2;
-
   // The distilled HTML.
   required string html = 3;
 
   message Image {
     // Handle to the image. This could be the URL where the image was found.
     // The handle should be referenced verbatim in the HTML.
     required string name = 1;
 
     // The image data
     required bytes data = 2;
   }
 
   // The images referenced in the HTML.
   repeated Image image = 4;
 }