[tracing] Allow enabling heap profiling from chrome://flags

chrome/browser/flag_descriptions.h

 // 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.
 
 #ifndef CHROME_BROWSER_FLAG_DESCRIPTIONS_H_
 #define CHROME_BROWSER_FLAG_DESCRIPTIONS_H_
 
 // Includes needed for macros allowing conditional compilation of some strings.
 #include "build/build_config.h"
 #include "build/buildflag.h"
@@ skipping 3305 matching lines @@
 extern const char kAutoplayPolicyUserGestureRequired[];
 
 // Name of the about: flag for displaying the title of the omnibox match for
 // current URL.
 extern const char kOmniboxDisplayTitleForCurrentUrlName[];
 
 // Description of the about: flag for displaying the title of the omnibox match
 // for current URL.
 extern const char kOmniboxDisplayTitleForCurrentUrlDescription[];
 
+// Name & description for the heap profiling flag.
+extern const char kEnableHeapProfilingName[];
+extern const char kEnableHeapProfilingDescription[];
+
+// Descriptions of the different heap profiling modes.
+extern const char kEnableHeapProfilingModePseudo[];
+extern const char kEnableHeapProfilingModeNative[];
+extern const char kEnableHeapProfilingTaskProfiler[];
+
 }  // namespace flag_descriptions
 
 #endif  // CHROME_BROWSER_FLAG_DESCRIPTIONS_H_