[MD settings] stream i18n replacement without large accumulation buffer

content/browser/webui/i18n_source_stream.h

 // Copyright 2016 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.
 
 #ifndef CONTENT_BROWSER_WEBUI_I18N_SOURCE_STREAM_H_
 #define CONTENT_BROWSER_WEBUI_I18N_SOURCE_STREAM_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 22 matching lines @@
 
   // SourceStream implementation.
   std::string GetTypeAsString() const override;
   int FilterData(net::IOBuffer* output_buffer,
                  int output_buffer_size,
                  net::IOBuffer* input_buffer,
                  int input_buffer_size,
                  int* consumed_bytes,
                  bool upstream_end_reached) override;
 
-  // Accumulated from upstream.
+  // Keep split $i18n tags (wait for the whole tag). This is expected to vary
+  // in size from 0 to a few KB and should never be larger than the input file
+  // (in the worst case).
   std::string input_;
 
-  // To send downstream.
+  // Keep excess that didn't fit in the output buffer. This is expected to vary
+  // in size from 0 to a few KB and should never get much larger than the input
+  // file (in the worst case).
   std::string output_;
 
-  // How much of the |output_| has been sent.
-  size_t drain_offset_;
-
   // A map of i18n replacement keys and translations.
   const ui::TemplateReplacements* replacements_;  // weak
 
   DISALLOW_COPY_AND_ASSIGN(I18nSourceStream);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_WEBUI_I18N_SOURCE_STREAM_H_