Add brotli content-encoding filter.

net/filter/filter.h

Index: net/filter/filter.h
diff --git a/net/filter/filter.h b/net/filter/filter.h
index 1904a8cdbb957be08b6baf3ef509d56a130a31ec..4b70558f9ff73e4e791692967edeaccc4ab1be12 100644
--- a/net/filter/filter.h
+++ b/net/filter/filter.h
@@ -128,6 +128,8 @@ class NET_EXPORT_PRIVATE FilterContext {
 
   // The BoundNetLog of the associated request.
   virtual const BoundNetLog& GetNetLog() const = 0;
+
+  virtual bool IsBrotliEnabled() const = 0;
 };
 
 //------------------------------------------------------------------------------
@@ -151,6 +153,7 @@ class NET_EXPORT_PRIVATE Filter {
 
   // Specifies type of filters that can be created.
   enum FilterType {
+    FILTER_TYPE_BROTLI,
     FILTER_TYPE_DEFLATE,
     FILTER_TYPE_GZIP,
     FILTER_TYPE_GZIP_HELPING_SDCH,  // Gzip possible, but pass through allowed.
@@ -231,6 +234,7 @@ class NET_EXPORT_PRIVATE Filter {
   std::string OrderedFilterList() const;
 
  protected:
+  friend class BrotliUnitTest;
   friend class GZipUnitTest;
   friend class SdchFilterChainingTest;
   FRIEND_TEST_ALL_PREFIXES(FilterTest, ThreeFilterChain);
@@ -283,6 +287,7 @@ class NET_EXPORT_PRIVATE Filter {
 
   // Helper methods for PrependNewFilter. If initialization is successful,
   // they return a fully initialized Filter. Otherwise, return NULL.
+  static Filter* InitBrotliFilter(FilterType type_id, int buffer_size);
   static Filter* InitGZipFilter(FilterType type_id, int buffer_size);
   static Filter* InitSdchFilter(FilterType type_id,
                                 const FilterContext& filter_context,