Update from https://crrev.com/305340

net/filter/sdch_filter.h

 // Copyright 2014 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.
 
 // SdchFilter applies open_vcdiff content decoding to a datastream.
 // This decoding uses a pre-cached dictionary of text fragments to decode
 // (expand) the stream back to its original contents.
 //
 // This SdchFilter internally uses open_vcdiff/vcdec library to do decoding.
 //
@@ skipping 25 matching lines @@
 
   // Decode the pre-filter data and writes the output into |dest_buffer|
   // The function returns FilterStatus. See filter.h for its description.
   //
   // Upon entry, *dest_len is the total size (in number of chars) of the
   // destination buffer. Upon exit, *dest_len is the actual number of chars
   // written into the destination buffer.
   FilterStatus ReadFilteredData(char* dest_buffer, int* dest_len) override;
 
  private:
-  // Internal status.  Once we enter an error state, we stop processing data.
+  // Internal status. Once we enter an error state, we stop processing data.
   enum DecodingStatus {
     DECODING_UNINITIALIZED,
     WAITING_FOR_DICTIONARY_SELECTION,
     DECODING_IN_PROGRESS,
     DECODING_ERROR,
     META_REFRESH_RECOVERY,  // Decoding error being handled by a meta-refresh.
     PASS_THROUGH,  // Non-sdch content being passed without alteration.
   };
 
   // Only to be instantiated by Filter::Factory.
@@ skipping 23 matching lines @@
   // ReadFilteredData.
   scoped_ptr<open_vcdiff::VCDiffStreamingDecoder> vcdiff_streaming_decoder_;
 
   // In case we need to assemble the hash piecemeal, we have a place to store
   // a part of the hash until we "get all 8 bytes plus a null."
   std::string dictionary_hash_;
 
   // After assembling an entire dictionary hash (the first 9 bytes of the
   // sdch payload, we check to see if it is plausible, meaning it has a null
   // termination, and has 8 characters that are possible in a net-safe base64
-  // encoding.  If the hash is not plausible, then the payload is probably not
+  // encoding. If the hash is not plausible, then the payload is probably not
   // an SDCH encoded bundle, and various error recovery strategies can be
   // attempted.
   bool dictionary_hash_is_plausible_;
 
-  // We hold an in-memory copy of the dictionary during the entire decoding, as
-  // it is used directly by the VC-DIFF decoding system.
-  // That char* data is part of the dictionary_ we hold a reference to.
-  scoped_refptr<SdchManager::Dictionary> dictionary_;
+  // Validity of this pointer is guaranteed by either the FilterContext holding
+  // a containing SdchManager::DictionarySet, or this object holding a
+  // container in |unexpected_dictionary_handle_| below.
+  const SdchManager::Dictionary *dictionary_;
 
   // We keep a copy of the URLRequestContext for use in the destructor, (at
   // which point GetURLRequestContext() will likely return null because of
-  // the disassociation of the URLRequest from the URLRequestJob).  This is
+  // the disassociation of the URLRequest from the URLRequestJob). This is
   // safe because the URLRequestJob (and any filters) are guaranteed to be
   // deleted before the URLRequestContext is destroyed.
   const URLRequestContext* const url_request_context_;
 
   // The decoder may demand a larger output buffer than the target of
   // ReadFilteredData so we buffer the excess output between calls.
   std::string dest_buffer_excess_;
   // To avoid moving strings around too much, we save the index into
   // dest_buffer_excess_ that has the next byte to output.
   size_t dest_buffer_excess_index_;
 
   // To get stats on activities, we keep track of source and target bytes.
   // Visit about:histograms/Sdch to see histogram data.
   size_t source_bytes_;
   size_t output_bytes_;
 
   // Error recovery in content type may add an sdch filter type, in which case
   // we should gracefully perform pass through if the format is incorrect, or
   // an applicable dictionary can't be found.
   bool possible_pass_through_;
 
   // The URL that is currently being filtered.
   // This is used to restrict use of a dictionary to a specific URL or path.
   GURL url_;
 
   // To facilitate error recovery, allow filter to know if content is text/html
   // by checking within this mime type (we may do a meta-refresh via html).
   std::string mime_type_;
 
+  // If the response was encoded with a dictionary different than those
+  // advertised (e.g. a cached response using an old dictionary), this
+  // variable preserves that dictionary from deletion during decoding.
+  scoped_ptr<SdchManager::DictionarySet> unexpected_dictionary_handle_;
+
   DISALLOW_COPY_AND_ASSIGN(SdchFilter);
 };
 
 }  // namespace net
 
 #endif  // NET_FILTER_SDCH_FILTER_H_