Do not apply gzip filter to file names with gz/tgz/svgz extensions.

net/base/filter.cc

 // 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.
 
 #include "net/base/filter.h"
 
+#include "base/file_path.h"
 #include "base/string_util.h"
 #include "net/base/gzip_filter.h"
 #include "net/base/bzip2_filter.h"
 #include "net/base/sdch_filter.h"
 
 namespace {
 
 // Filter types (using canonical lower case only):
 const char kDeflate[]      = "deflate";
 const char kGZip[]         = "gzip";
@@ skipping 69 matching lines @@
   if ((1 == encoding_types->size()) &&
       (FILTER_TYPE_GZIP == encoding_types->front())) {
     if (LowerCaseEqualsASCII(mime_type, kApplicationXGzip) ||
         LowerCaseEqualsASCII(mime_type, kApplicationGzip) ||
         LowerCaseEqualsASCII(mime_type, kApplicationXGunzip))
       // The server has told us that it sent us gziped content with a gzip
       // content encoding.  Sadly, Apache mistakenly sets these headers for all
       // .gz files.  We match Firefox's nsHttpChannel::ProcessNormal and ignore
       // the Content-Encoding here.
       encoding_types->clear();
+
+    GURL url;
+    success = filter_context.GetURL(&url);
+    DCHECK(success);
+    FilePath filename = FilePath().AppendASCII(url.ExtractFileName());
+    FilePath::StringType extension = filename.Extension();
+
+    // Firefox does not apply the filter to the following extensions.
+    // See Firefox's nsHttpChannel::nsContentEncodings::GetNext() and
+    // nonDecodableExtensions in nsExternalHelperAppService.cpp
+    if (0 == extension.compare(FILE_PATH_LITERAL(".gz")) ||
+        0 == extension.compare(FILE_PATH_LITERAL(".tgz")) ||
+        0 == extension.compare(FILE_PATH_LITERAL(".svgz"))) {
+      encoding_types->clear();
+    }
   }
 
   if (!filter_context.IsSdchResponse()) {
     if (1 < encoding_types->size()) {
       // Multiple filters were intended to only be used for SDCH (thus far!)
       SdchManager::SdchErrorRecovery(
           SdchManager::MULTIENCODING_FOR_NON_SDCH_REQUEST);
     }
     if ((1 == encoding_types->size()) &&
         (FILTER_TYPE_SDCH == encoding_types->front())) {
@@ skipping 232 matching lines @@
 
   DCHECK(stream_buffer());
   // Bail out if there is more data in the stream buffer to be filtered.
   if (!stream_buffer() || stream_data_len_)
     return false;
 
   next_stream_data_ = stream_buffer()->data();
   stream_data_len_ = stream_data_len;
   return true;
 }