Make gtk2/gtk3 compile time switchable.

remoting/remoting_host.gypi

 # Copyright (c) 2012 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.
 
 {
   'includes': [
     'remoting_enable.gypi',
   ],
 
   'conditions': [
@@ skipping 54 matching lines @@
                     '../build/linux/system.gyp:xext',
                     '../build/linux/system.gyp:xfixes',
                     '../build/linux/system.gyp:xi',
                     '../build/linux/system.gyp:xrandr',
                     '../build/linux/system.gyp:xtst',
                   ],
                 }],
                 ['chromeos==0 and use_ozone==0', {
                   'dependencies': [
                     # use GTK on Linux, even for Aura builds.
-                    '../build/linux/system.gyp:gtk',
+                    '../build/linux/system.gyp:gtk2',
                   ],
                 }]
               ],
             }],
             ['chromeos==1', {
               'dependencies' : [
                 '../cc/cc.gyp:cc',
                 '../gpu/gpu.gyp:command_buffer_common',
                 '../ppapi/ppapi_internal.gyp:ppapi_host',
                 '../skia/skia.gyp:skia',
@@ skipping 581 matching lines @@
               ],
               'sources': [
                 'host/it2me/it2me_native_messaging_host_entry_point.cc',
                 'host/it2me/it2me_native_messaging_host_main.cc',
                 'host/it2me/it2me_native_messaging_host_main.h',
               ],
               'conditions': [
                 ['OS=="linux" and chromeos==0 and use_ozone==0', {
                   'dependencies': [
                     # Always use GTK on Linux, even for Aura builds.
-                    '../build/linux/system.gyp:gtk',
+                    '../build/linux/system.gyp:gtk2',
                   ],
                 }],
                 ['OS=="linux" and use_allocator!="none"', {
                   'dependencies': [
                     '../base/allocator/allocator.gyp:allocator',
                   ],
                 }],
                 ['OS=="mac"', {
                   'mac_bundle': 1,
                   'variables': {
@@ skipping 61 matching lines @@
               # Dummy target for chromeos==1
               'target_name': 'remoting_it2me_native_messaging_host',
               'type': 'executable',
             },
           ],  # targets
         }],  # end of chromeos==0
       ],  # end of conditions
     }],  # end of OS!="win" and enable_remoting_host==1
   ],  # end of 'conditions'
 }