Hand craft an A/B test of SDCH compression...

net/base/filter.h

 // Copyright (c) 2006-2008 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();
@@ skipping 30 matching lines @@
 
 //------------------------------------------------------------------------------
 // Define an interface class that allows access to contextual information
 // supplied by the owner of this filter.  In the case where there are a chain of
 // filters, there is only one owner of all the chained filters, and that context
 // is passed to the constructor of all those filters.  To be clear, the context
 // does NOT reflect the position in a chain, or the fact that there are prior
 // or later filters in a chain.
 class FilterContext {
  public:
+  // Enum to control what histograms are emitted near end-of-life of this
+  // instance.
+  enum StatisticSelector {
+    SDCH_DECODE,
+    SDCH_PASSTHROUGH,
+    SDCH_EXPERIMENT_DECODE,
+    SDCH_EXPERIMENT_HOLDBACK,
+  };
+
   virtual ~FilterContext() {}
 
   // What mime type was specified in the header for this data?
   // Only makes senses for some types of contexts, and returns false
   // when not applicable.
   virtual bool GetMimeType(std::string* mime_type) const = 0;
 
   // What URL was used to access this data?
   // Return false if gurl is not present.
   virtual bool GetURL(GURL* gurl) const = 0;
@@ skipping 17 matching lines @@
   // What response code was received with the associated network transaction?
   // For example: 200 is ok.   4xx are error codes. etc.
   virtual int GetResponseCode() const = 0;
 
   // What is the desirable input buffer size for these filters?
   // This value is currently supplied by the context, and is constant for all
   // filters, even when they are part of a chain of filters. (i.e., we currently
   // don't change the input buffer sizes for a linked chain of filters, and the
   // buffer size for input to all filters in a chain is this one constant).
   virtual int GetInputStreamBufferSize() const = 0;
+
+  // The following method forces the context to emit a specific set of
+  // statistics as selected by the argument.
+  virtual void RecordPacketStats(StatisticSelector statistic) const = 0;
 };
 
 //------------------------------------------------------------------------------
 class Filter {
  public:
   // Return values of function ReadFilteredData.
   enum FilterStatus {
     // Read filtered data successfully
     FILTER_OK,
     // Read filtered data successfully, and the data in the buffer has been
@@ skipping 74 matching lines @@
 
   // Given a array of encoding_types, try to do some error recovery adjustment
   // to the list.  This includes handling known bugs in the Apache server (where
   // redundant gzip encoding is specified), as well as issues regarding SDCH
   // 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:
   explicit Filter(const FilterContext& filter_context);
 
   FRIEND_TEST(SdchFilterTest, ContentTypeId);
   // 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 49 matching lines @@
 
   // Context data from the owner of this filter.  Some filters need additional
   // context information (mime type, etc.) to properly function, and they access
   // this data via this reference member.
   const FilterContext& filter_context_;
 
   DISALLOW_COPY_AND_ASSIGN(Filter);
 };
 
 #endif  // NET_BASE_FILTER_H__