Mojo JS bindings: specify compress="gzip" for bindings JS files in .grd.

ui/webui/resources/webui_resources.grd

 <?xml version="1.0" encoding="UTF-8"?>
 <!-- This comment is only here because changes to resources are not picked up
 without changes to the corresponding grd file. -->
 <grit latest_public_release="0" current_release="1" output_all_resource_defines="false">
   <outputs>
     <output filename="grit/webui_resources.h" type="rc_header">
       <emit emit_type='prepend'></emit>
     </output>
     <output filename="grit/webui_resources_map.cc"
             type="resource_file_map_source" />
     <output filename="grit/webui_resources_map.h" type="resource_map_header" />
     <output filename="webui_resources.pak" type="data_package" />
   </outputs>
   <release seq="1">
     <includes>
       <include name="IDR_WEBUI_I18N_TEMPLATE_JS" file="js/i18n_template.js" flattenhtml="true" type="BINDATA" />
       <include name="IDR_WEBUI_JSTEMPLATE_JS" file="js/jstemplate_compiled.js" flattenhtml="true" type="BINDATA" />
       <include name="IDR_WEBUI_ANALYTICS_JS" file="js/analytics.js" flattenhtml="true" type="BINDATA" />
       <include name="IDR_WEBUI_MOJO_BINDINGS_JS"
                file="${root_gen_dir}\mojo\public\js\mojo_bindings.js"
-               flattenhtml="true" type="BINDATA" use_base_dir="false" />
+               flattenhtml="true" type="BINDATA" use_base_dir="false" compress="gzip" />
       <!-- Roboto Font. Roboto-Regular and Roboto-Light is already available on
            Android, and Roboto-Medium is not used on Android. All 6 weights of
            Roboto are available on Chrome OS.-->
       <if expr="not is_android and not chromeos">
         <include name="IDR_WEBUI_ROBOTO_ROBOTO_REGULAR_WOFF2" file="roboto/roboto-regular.woff2" type="BINDATA" />
         <include name="IDR_WEBUI_ROBOTO_ROBOTO_MEDIUM_WOFF2" file="roboto/roboto-medium.woff2" type="BINDATA" />
         <include name="IDR_WEBUI_ROBOTO_ROBOTO_BOLD_WOFF2" file="roboto/roboto-bold.woff2" type="BINDATA" />
       </if>
 
       <!-- Component apps common image resources - 1x -->
@@ skipping 473 matching lines @@
                    file="js/chromeos/ui_account_tweaks.js"
                    type="chrome_html" />
       </if>
       <if expr="not is_android">
         <part file="cr_elements_resources.grdp" />
         <part file="polymer_resources.grdp" />
       </if>
     </structures>
   </release>
 </grit>