Add an extension override bubble and warning box for proxy extensions.

chrome/browser/resources/options/browser_options.html

 <div id="settings" class="page" hidden>
   <header>
     <h1 i18n-content="settingsTitle"></h1>
   </header>
   <include src="reset_profile_settings_banner.html">
   <include src="automatic_settings_reset_banner.html">
 <if expr="chromeos">
   <include src="secondary_user_banner.html">
   <section>
     <div id="network-section-header" class="section-header">
@@ skipping 12 matching lines @@
       </div>
       <div id="network-menus"></div>
     </div>
   </section>
 </if>
 <if expr="not chromeos">
   <include src="sync_section.html">
   <include src="startup_section.html">
 </if>
   <section>
+    <h3 id="proxy-section" i18n-content="sectionTitleProxy" hidden></h3>

[Dan Beam, 2014/05/20 16:46:41]

can you hide the whole <section> instead?

[Finnur, 2014/05/21 16:30:32]

Indeed.

+    <div id="proxy-section-content"></div>
+  </section>
+
+  <section>
     <h3 i18n-content="sectionTitleAppearance"></h3>
     <div class="settings-row">
 <if expr="chromeos">
       <button id="set-wallpaper" i18n-content="setWallpaper"
           guest-visibility="disabled"></button>
       <span id="wallpaper-indicator" class="controlled-setting-indicator">
       </span>
 </if>
 <if expr="not chromeos and is_posix and not is_macosx">
       <button id="themes-gallery" i18n-content="themesGallery"></button>
@@ skipping 506 matching lines @@
           <span i18n-content="tabsToLinksPref"></span>
         </label>
       </div>
 </if>
     </div>
   </section>
 <if expr="not chromeos">
   <section id="network-section">
     <h3 i18n-content="advancedSectionTitleNetwork"></h3>
     <div>
-      <span id="proxiesLabel" class="settings-row"></span>
+      <span id="proxiesLabel"
+            class="settings-row"
+            i18n-content="proxiesLabelSystem"></span>
       <div class="settings-row">
         <button id="proxiesConfigureButton"
             i18n-content="proxiesConfigureButton"></button>
         <span class="controlled-setting-indicator" pref="proxy" plural></span>
       </div>
     </div>
   </section>
 </if>
   <section id="languages-section">
     <h3 i18n-content="advancedSectionTitleLanguages"></h3>
@@ skipping 356 matching lines @@
     </div>
   </section>
   </div>  <!-- advanced-settings-container -->
   </div>  <!-- advanced-settings -->
   <footer>
     <button id="advanced-settings-expander" class="link-button"
         i18n-content="showAdvancedSettings">
     </button>
   </footer>
   </div>