Update from https://crrev.com/302630

net/filter/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.
 //
 // Filter performs filtering on data streams. Sample usage:
 //
 //   IStream* pre_filter_source;
 //   ...
 //   Filter* filter = Filter::Factory(filter_type, size);
 //   int pre_filter_data_len = filter->stream_buffer_size();
 //   pre_filter_source->read(filter->stream_buffer(), pre_filter_data_len);
 //
 //   filter->FlushStreamBuffer(pre_filter_data_len);
 //
 //   char post_filter_buf[kBufferSize];
 //   int post_filter_data_len = kBufferSize;
 //   filter->ReadFilteredData(post_filter_buf, &post_filter_data_len);
 //
 // To filter a data stream, the caller first gets filter's stream_buffer_
 // through its accessor and fills in stream_buffer_ with pre-filter data, next
 // calls FlushStreamBuffer to notify Filter, then calls ReadFilteredData
-// repeatedly to get all the filtered data. After all data have been fitlered
-// and read out, the caller may fill in stream_buffer_ again. This
+// repeatedly to get all the filtered data. After all data have been filtered
+// and read out, the caller may fill in stream_buffer_ again.  This
 // WriteBuffer-Flush-Read cycle is repeated until reaching the end of data
 // stream.
 //
+// A return of FILTER_OK from ReadData() means that more data is
+// available to a future ReadData() call and data may not be written
+// into stream_buffer().  A return of FILTER_NEED_MORE_DATA from ReadData()
+// indicates that no data will be forthcoming from the filter until
+// it receives more input data, and that the buffer at
+// stream_buffer() may be written to.
+//
+// The filter being complete (no more data to provide) may be indicated
+// by either returning FILTER_DONE or by returning FILTER_OK and indicating
+// zero bytes output; consumers understand both those signals.  Consumers
+// are responsible for not calling ReadData() on a filter after one of these
+// signals have been returned.  Note that some filters may never signal that
+// they are done (e.g. a pass-through filter will always
+// say FILTER_NEED_MORE_DATA), so the consumer will also need to
+// recognize the state of |no_more_input_data_available &&
+// filter->stream_data_len() == 0| as FILTER_DONE.
+//
 // The lifetime of a Filter instance is completely controlled by its caller.
 
 #ifndef NET_FILTER_FILTER_H__
 #define NET_FILTER_FILTER_H__
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/gtest_prod_util.h"
@@ skipping 163 matching lines @@
   // encoding, where various proxies and anti-virus products modify or strip the
   // encodings.  These fixups require context, which includes whether this
   // response was made to an SDCH request (i.e., an available dictionary was
   // advertised in the GET), as well as the mime type of the content.
   static void FixupEncodingTypes(const FilterContext& filter_context,
                                  std::vector<FilterType>* encoding_types);
 
  protected:
   friend class GZipUnitTest;
   friend class SdchFilterChainingTest;
+  FRIEND_TEST_ALL_PREFIXES(FilterTest, ThreeFilterChain);
 
   Filter();
 
   // Filters the data stored in stream_buffer_ and writes the output into the
   // dest_buffer passed in.
   //
   // 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.
   //
@@ skipping 55 matching lines @@
   // Remember what status or local filter last returned so we can better handle
   // chained filters.
   FilterStatus last_status_;
 
   DISALLOW_COPY_AND_ASSIGN(Filter);
 };
 
 }  // namespace net
 
 #endif  // NET_FILTER_FILTER_H__