Tell V8 about the extra memory being held by FileReader objects.

third_party/WebKit/Source/core/fileapi/FileReaderLoader.h

 /*
  * Copyright (C) 2010 Google Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 94 matching lines @@
 
   FileError::ErrorCode GetErrorCode() const { return error_code_; }
 
   void SetEncoding(const String&);
   void SetDataType(const String& data_type) { data_type_ = data_type; }
 
  private:
   FileReaderLoader(ReadType, FileReaderLoaderClient*);
 
   void Cleanup();
+  void ReportAdditionalMemoryUsageToV8(int64_t usage);
+  void UnreportMemoryUsageToV8();
 
   void Failed(FileError::ErrorCode);
-  void ConvertToText();
-  void ConvertToDataURL();
+  String ConvertToText();
+  String ConvertToDataURL();
+  void SetStringResult(const String&);
 
   static FileError::ErrorCode HttpStatusCodeToErrorCode(int);
 
   ReadType read_type_;
   FileReaderLoaderClient* client_;
   WTF::TextEncoding encoding_;
   String data_type_;
 
   KURL url_for_reading_;
   Persistent<ThreadableLoader> loader_;
 
   std::unique_ptr<ArrayBufferBuilder> raw_data_;
   bool is_raw_data_converted_;
 
   Persistent<DOMArrayBuffer> array_buffer_result_;
   String string_result_;
 
   // The decoder used to decode the text data.
   std::unique_ptr<TextResourceDecoder> decoder_;
 
   bool finished_loading_;
   long long bytes_loaded_;
   // If the total size of the resource is unknown, m_totalBytes is set to -1
   // until completion of loading, and the buffer for receiving data is set to
   // dynamically grow. Otherwise, m_totalBytes is set to the total size and
   // the buffer for receiving data of m_totalBytes is allocated and never grow
   // even when extra data is appeneded.
   long long total_bytes_;
-
+  int64_t memory_usage_reported_to_v8_ = 0;

[michaeln, 2017/04/28 00:54:25]

i can switch more of the data members to initialize here too

[dmurph, 2017/04/28 20:39:44]

That would be great actually. I like that style.

   bool has_range_;
   unsigned range_start_;
   unsigned range_end_;
 
   FileError::ErrorCode error_code_;
 };
 
 }  // namespace blink
 
 #endif  // FileReaderLoader_h