Enable gtk3 for 32-bit builds

Now that [1] has been fixed and libgtk-3-0 has been installed in
clusterfuzz's 32-bit configuration, it's safe to enable gtk3 for all
platforms.

[1] https://crbug.com/699669

BUG=79722
TBR=dpranke@chromium.org
CC=erg@chromium.org,inferno@chromium.org

Review-Url: https://codereview.chromium.org/2847863002
Cr-Original-Commit-Position: refs/heads/master@{#468110}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 94297f25fdf492db4eedd9524c413c7566994567
diff --git a/config/linux/gtk/gtk.gni b/config/linux/gtk/gtk.gni
index 0521a8c..53e943e 100644
--- a/config/linux/gtk/gtk.gni
+++ b/config/linux/gtk/gtk.gni
@@ -8,8 +8,5 @@
 
 declare_args() {
   # Whether to compile against GTKv3 instead of GTKv2.
-  # TODO(thomasanderson): Currently, the 32-bit clusterfuzz schroot does not
-  # have libgtk-3-0 installed.  set use_gtk3 = true on all architectures when
-  # the package is added (crbug.com/699669).
-  use_gtk3 = target_cpu == "x64"
+  use_gtk3 = true
 }