Make gtk2/gtk3 compile time switchable.

chrome/browser/ui/libgtk2ui/libgtk2ui.gyp

Index: chrome/browser/ui/libgtk2ui/libgtk2ui.gyp
diff --git a/chrome/browser/ui/libgtk2ui/libgtk2ui.gyp b/chrome/browser/ui/libgtk2ui/libgtk2ui.gyp
index d3e3004bed890e3218d2f4b087448ab17fdbbbbc..2d219fd1647cd7f0164cdb5bf2590f9be453a739 100644
--- a/chrome/browser/ui/libgtk2ui/libgtk2ui.gyp
+++ b/chrome/browser/ui/libgtk2ui/libgtk2ui.gyp
@@ -16,8 +16,6 @@
         '../../../../base/base.gyp:base_i18n',
         '../../../../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
         '../../../../build/linux/system.gyp:gconf',
-        '../../../../build/linux/system.gyp:gtk',
-        '../../../../build/linux/system.gyp:gtkprint',
         '../../../../build/linux/system.gyp:x11',
         '../../../../components/components_resources.gyp:components_resources',
         '../../../../content/content.gyp:content',
@@ -106,6 +104,17 @@
             'gconf_listener.h',
           ],
         }],
+        ['use_gtk3==1', {
+          'dependencies': [
+            '../../../../build/linux/system.gyp:gtk3',
+            '../../../../build/linux/system.gyp:gtkprint3',
+          ],
+        }, {
+          'dependencies': [
+            '../../../../build/linux/system.gyp:gtk2',
+            '../../../../build/linux/system.gyp:gtkprint2',
+          ],
+        }],
         [ 'clang==1', {
           'cflags': [
             # G_DEFINE_TYPE automatically generates a *get_instance_private inline function after glib 2.37.