Fix gtk3 build

remoting/host/BUILD.gn

 # Copyright 2014 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.
 
 import("//remoting/build/config/remoting_build.gni")
 
 process_version("remoting_version") {
   template_file = "//remoting/host/version.h.in"
   sources = [
     branding_path,
@@ skipping 393 matching lines @@
   if (is_linux && !is_chromeos) {
     libs += [ "pam" ]
   }
 
   if (use_x11) {
     configs += [
       "//build/config/linux:x11",
       "//build/config/linux:xrandr",
     ]
     if (is_desktop_linux) {
-      deps += [ "//build/config/linux/gtk2" ]
+      if (use_gtk3) {
+        deps += [ "//build/config/linux/gtk3" ]
+      } else {
+        deps += [ "//build/config/linux/gtk2" ]
+      }
     }
   } else {
     sources -= [
       "clipboard_x11.cc",
       "desktop_resizer_x11.cc",
       "input_injector_x11.cc",
       "local_input_monitor_x11.cc",
     ]
     if (is_linux) {
       # These will already be filtered out on non-Linux.
@@ skipping 722 matching lines @@
 
     if (enable_webrtc) {
       deps += [
         "//third_party/libjingle:libjingle_webrtc",
         "//third_party/webrtc/libjingle/xmllite",
         "//third_party/webrtc/libjingle/xmpp",
       ]
     }
 
     if (is_desktop_linux) {
-      deps += [ "//build/config/linux/gtk2" ]
+      if (use_gtk3) {
+        deps += [ "//build/config/linux/gtk3" ]
+      } else {
+        deps += [ "//build/config/linux/gtk2" ]
+      }
     }
     if ((is_linux && !is_chromeos) || is_mac) {
       libs = [ "pam" ]
     }
 
     if (is_mac && is_official_build) {
       sources += [ "internal/internal_mac-inl.h" ]
       defines += [ "USE_REMOTING_MACOSX_INTERNAL" ]
     }
 
@@ skipping 733 matching lines @@
                       root_build_dir),
           rebase_path(outputs[0], root_build_dir),
         ]
       }
     } else {
       group("remoting_host_installation") {
       }
     }
   }
 }