Turn on navigator.registerProtocolHandler().

build/common.gypi

 # Copyright (c) 2011 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 111 matching lines @@
       # it can be overriden by the GYP command line or by ~/.gyp/include.gypi.
       'component%': 'static_library',
 
       # Set to select the Title Case versions of strings in GRD files.
       'use_titlecase_in_grd_files%': 0,
 
       # Use translations provided by volunteers at launchpad.net.  This
       # currently only works on Linux.
       'use_third_party_translations%': 0,
 
-      # Enable the Manage Handlers section in the settings page.
-      'enable_register_protocol_handler%': 0,
+      # Enable navigator.registerProtocolHandler and supporting UI.
+      'enable_register_protocol_handler%': 1,
 
       # Remoting compilation is enabled by default. Set to 0 to disable.
       'remoting%': 1,
 
       # P2P APIs are compiled in by default. Set to 0 to disable.
       # Also note that this should be enabled for remoting to compile.
       'p2p_apis%': 1,
 
       # If this is set, the clang plugins used on the buildbot will be used.
       # Run tools/clang/scripts/update.sh to make sure they are compiled.
@@ skipping 1599 matching lines @@
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }
 
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