[MD settings] stream i18n replacement without large accumulation buffer

content/browser/webui/i18n_source_stream.h

Index: content/browser/webui/i18n_source_stream.h
diff --git a/content/browser/webui/i18n_source_stream.h b/content/browser/webui/i18n_source_stream.h
index 0f37d874869a2f6e9737af88fa193d8266a89b0e..64378c85f3099a85f17fdbef06bdaa4e76e2d510 100644
--- a/content/browser/webui/i18n_source_stream.h
+++ b/content/browser/webui/i18n_source_stream.h
@@ -40,15 +40,16 @@ class CONTENT_EXPORT I18nSourceStream : public net::FilterSourceStream {
                  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