chromeos: Increase WebUI font size to 80% for Roboto.

ui/strings/app_locale_settings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 <grit latest_public_release="0" current_release="1">
   <outputs>
     <output filename="grit/app_locale_settings.h" type="rc_header">
       <emit emit_type='prepend'></emit>
     </output>
     <output filename="app_locale_settings_am.pak" type="data_package" lang="am" />
     <output filename="app_locale_settings_ar.pak" type="data_package" lang="ar" />
     <if expr="use_third_party_translations">
       <output filename="app_locale_settings_ast.pak" type="data_package" lang="ast" />
@@ skipping 236 matching lines @@
           Arial, sans-serif
         </message>
 
         <!-- The relative font size in % used in Web UI (e.g. History).  -->
         <message name="IDS_WEB_FONT_SIZE" use_name_for_id="true">
           75%
         </message>
       </if>
       <!-- For Chrome OS -->
       <if expr="chromeos">
-        <!-- The font name like: 'Font Name, 10' -->
+        <!-- The font name like: 'Font Name, 12px' -->
         <message name="IDS_UI_FONT_FAMILY_CROS" use_name_for_id="true">
           Noto Sans UI, 13px
         </message>
 
         <!-- The font used in Web UI (e.g. History). -->
         <message name="IDS_WEB_FONT_FAMILY" use_name_for_id="true">
           'Noto Sans UI', sans-serif
         </message>
 
         <!-- The relative font size in % used in Web UI (e.g. History).  -->
+        <!-- TODO(xdai): 80% is an appropriate size for Roboto, which is the
+             default as of M42, rather than for Noto Sans UI. This comment
+             should be deleted when the old Noto Sans UI code is removed; see
+             http://crbug.com/482042. -->
         <message name="IDS_WEB_FONT_SIZE" use_name_for_id="true">
-          75%
+          80%
         </message>
       </if>
     </messages>
   </release>
 </grit>