Fix gtk3 build

remoting/host/BUILD.gn

Index: remoting/host/BUILD.gn
diff --git a/remoting/host/BUILD.gn b/remoting/host/BUILD.gn
index fd1745dc51e5f3963f5c483aa2f10deb425215e6..6b3f87c52f5eb1e52d02f144b92111fb804c0698 100644
--- a/remoting/host/BUILD.gn
+++ b/remoting/host/BUILD.gn
@@ -411,7 +411,11 @@ static_library("host") {
       "//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 -= [
@@ -1154,7 +1158,11 @@ if (enable_me2me_host) {
     }
 
     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" ]