Add an experiment to avoid memory pressure broadcasts.

chrome/browser/flag_descriptions.cc

 // Copyright 2017 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 "chrome/browser/flag_descriptions.h"
 
 namespace flag_descriptions {
 
 //  Material Design version of chrome://bookmarks
 
@@ skipping 3116 matching lines @@
     "Enable an experimental change for Location.reload() to trigger a "
     "hard-reload.";
 
 const char kCaptureThumbnailOnLoadFinishedName[] =
     "Capture page thumbnail on load finished";
 
 const char kCaptureThumbnailOnLoadFinishedDescription[] =
     "Capture a page thumbnail (for use on the New Tab page) when the page load "
     "finishes, in addition to other times a thumbnail may be captured.";
 
+const char kEnableBroadcastMemoryPressureName[] =
+    "Enables broadcasting memory pressure notifications to renderers.";
+const char kEnableBroadcastMemoryPressureDescription[] =
+    "When enabled, all renderers will be notified of system memory pressure "
+    "events and will perfom some memory optimizations.";
+
 }  // namespace flag_descriptions