Options: add a "Learn more" link to Android Apps section and tweak strings

chrome/browser/resources/options/browser_options.html

 <div id="settings" class="page" hidden>
   <header>
     <h1 i18n-content="settingsTitle"></h1>
   </header>
   <include src="automatic_settings_reset_banner.html">
 <if expr="chromeos">
   <link rel="import" href="chrome://resources/cr_elements/network/cr_network_icon.html">
   <link rel="import" href="chrome://resources/cr_elements/network/cr_onc_types.html">
   <include src="secondary_user_banner.html">
   <section id="network-section-cros">
@@ skipping 219 matching lines @@
     <div class="checkbox controlled-setting-with-label">
       <label>
         <input id="android-apps-enabled" pref="arc.enabled"
             metric="Options_AndroidApps" type="checkbox" dialog-pref>
         <span>
           <span i18n-content="androidAppsEnabled"></span>
           <span class="controlled-setting-indicator"
                 pref="arc.enabled"></span>
         </span>
       </label>
+      <a target="_blank" i18n-content="learnMore"
+          href="http://support.google.com/chromebook?p=playapps"></a>
     </div>
     <div id="android-apps-settings" class="controlled-setting-with-label" hidden>
       <label>
         <span id="android-apps-settings-label"></span>
       </label>
     </div>
   </section>
 </if>
   <section id="sync-users-section" guest-visibility="hidden">
     <h3 i18n-content="sectionTitleUsers"></h3>
@@ skipping 112 matching lines @@
       <div class="settings-row">
         <button id="privacyContentSettingsButton"
             i18n-content="privacyContentSettingsButton"></button>
         <button id="privacyClearDataButton"
             i18n-content="privacyClearDataButton"></button>
       </div>
       <p id="privacy-explanation" class="settings-row">
         <span i18n-content="improveBrowsingExperience"></span>
         <span i18n-content="disableWebServices"></span>
         <a target="_blank" i18n-content="learnMore"
             i18n-values="href:privacyLearnMoreURL"></a>

[Dan Beam, 2016/06/24 22:30:17]

I just pasted the URL directly into the HTML because there's really no reason
not to if:

a) the link isn't translated (i.e. ?hl=[LANGCODE], we don't do that any more)
b) it doesn't vary per-platform (i.e. it's ChromeOS-only)

the link I'm adding satisfies both, just like the a11y one above, so I'm just
slapping it in the HTML

       </p>
       <div class="checkbox controlled-setting-with-label">
         <label>
           <input id="alternateErrorPagesEnabled"
               pref="alternate_error_pages.enabled"
               metric="Options_LinkDoctorCheckbox" type="checkbox">
           <span>
             <span i18n-content="linkDoctorPref"></span>
             <span class="controlled-setting-indicator"
                 pref="alternate_error_pages.enabled"></span>
@@ skipping 417 matching lines @@
 </if>
 
 <if expr="chromeos">
   <include src="startup_section.html">
 </if>
 
 <section id="a11y-section">
   <h3 i18n-content="accessibilityTitle"></h3>
 
   <div>
     <a href="https://chrome.google.com/webstore/category/collection/accessibility"

[Dan Beam, 2016/06/24 22:30:17]

^ just like this one

         id="accessibility-features" target="_blank"
         i18n-content="accessibilityFeaturesLink"></a>
   </div>
 
 <if expr="chromeos">
   <div class="option-control-table">
     <p id="accessibility-explanation" class="settings-row">
       <span i18n-content="accessibilityExplanation"></span>
       <a id="accessibility-learn-more" target="_blank"
           i18n-values="href:accessibilityLearnMoreURL"
@@ skipping 299 matching lines @@
       </button>
     </div>
   </section>
   </div>  <!-- advanced-settings-container -->
   </div>  <!-- advanced-settings -->
   <footer id="advanced-settings-footer">
     <a is="action-link" id="advanced-settings-expander"
         i18n-content="showAdvancedSettings"></a>
   </footer>
 </div>