[DocWriteBlocking] Add feature to block doc.written scripts if 2g-like network

content/public/common/content_features.cc

 // Copyright 2015 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 "build/build_config.h"
 #include "content/public/common/content_features.h"
 
 namespace features {
 
 // All features in alphabetical order.
 
+// Blocks scripts inserted by document.write if the connection is 2g-esque.
+const base::Feature kBlockDocWriteIfEffectively2G{
+    "BlockDocWriteIfEffectively2G", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Enables brotli "Accept-Encoding" advertising and "Content-Encoding" support.
 // Brotli format specification: http://www.ietf.org/id/draft-alakuijala-brotli
 const base::Feature kBrotliEncoding{"brotli-encoding",
                                     base::FEATURE_ENABLED_BY_DEFAULT};
 
 // If Canvas2D Image Chromium is allowed, this feature controls whether it is
 // enabled.
 const base::Feature kCanvas2DImageChromium{"Canvas2DImageChromium",
                                            base::FEATURE_ENABLED_BY_DEFAULT};
 
@@ skipping 162 matching lines @@
 #endif
 
 #if defined(OS_WIN)
 // Emergency "off switch" for new Windows sandbox security mitigation,
 // sandbox::MITIGATION_EXTENSION_POINT_DISABLE.
 const base::Feature kWinSboxDisableExtensionPoints{
     "WinSboxDisableExtensionPoint", base::FEATURE_ENABLED_BY_DEFAULT};
 #endif
 
 }  // namespace features