Update some strings in the options dialog w.r.t. themes.

chrome/app/generated_resources.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!-- This file contains definitions of resources that will be translated for
 each locale. -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
       source_lang_id="en" enc_check="möl">
   <outputs>
     <output filename="grit/generated_resources.h" type="rc_header">
       <emit emit_type='prepend'></emit>
@@ skipping 3987 matching lines @@
       <message name="IDS_OPTIONS_AUTOFILL_SAVE" desc="The label of the 'Ask me to save autofill' radio button">
         Save text from forms to make them easier to fill out
       </message>
       <message name="IDS_OPTIONS_AUTOFILL_NEVERSAVE" desc="The label of the 'Never save autofill' radio button">
         Never save text from forms
       </message>
 
       <message name="IDS_THEMES_GROUP_NAME" desc="The title of the themes group">
         Themes:
       </message>
-      <message name="IDS_THEMES_GTK_BUTTON" desc="The button to choose GTK colors and icons as the current theme.">
-        Set to GTK+ theme
-      </message>
-      <message name="IDS_THEMES_SET_CLASSIC" desc="The button to choose the classic windows theme in GTK">
-            Set to Classic theme
-      </message>
+      <if expr="os == 'linux2'">
+        <message name="IDS_APPEARANCE_GROUP_NAME" desc="The title of the themes group">
+          Appearance:
+        </message>
+        <message name="IDS_THEMES_GTK_BUTTON" desc="The button to choose GTK colors and icons as the current theme.">
+          Use GTK+ theme
+        </message>
+        <message name="IDS_THEMES_SET_CLASSIC" desc="The button to choose the classic windows theme in GTK">
+          Use Classic theme
+        </message>
+      </if>
       <message name="IDS_THEMES_RESET_BUTTON" desc="The button to reset your theme">
         Reset to default theme
       </message>
       <message name="IDS_THEMES_DEFAULT_THEME_LABEL" desc="The label describing the default theme">
         Default
       </message>
       <message name="IDS_THEMES_GALLERY_BUTTON" desc="The button to get more themes">
         Get themes
       </message>
 
@@ skipping 1512 matching lines @@
         Speed Sensitivity:
       </message>
       <message name="IDS_STATUSBAR_NO_NETWORKS_MESSAGE" desc="No networks are available">
         Speed Sensitivity:
       </message>
     </if>
 
     </messages>
   </release>
 </grit>