Convert remaining instances of the 'os' variable in grit conditions

chrome/app/google_chrome_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 <!-- This file contains definitions of strings that are specific to
 Google Chrome. These strings will be translated for each locale that Google
 Chrome supports. -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
       source_lang_id="en" enc_check="möl">
   <outputs>
     <output filename="grit/google_chrome_strings.h" type="rc_header">
       <emit emit_type='prepend'></emit>
@@ skipping 174 matching lines @@
         Google Chrome Canary
       </message>
       <message name="IDS_PRODUCT_DESCRIPTION" desc="Browser description">
         Google Chrome is a web browser that runs web pages and applications with lightning speed. It's fast, stable, and easy to use. Browse the web more safely with malware and phishing protection built into Google Chrome.
       </message>
       <if expr="pp_ifdef('chromeos')">
         <message name="IDS_PRODUCT_OS_NAME" desc="The Chrome OS application name">
           Chrome OS
         </message>
       </if>
-      <if expr="os.find('win') != -1">
+      <if expr="is_win">
         <message name="IDS_PRODUCT_FRAME_NAME" desc="The Chrome Frame application name">
           Google Chrome Frame
         </message>
         <message name="IDS_VERSIONMISMATCH_HEADER">
           Chrome Frame Update.
         </message>
         <message name="IDS_VERSIONMISMATCH">
           Chrome Frame has been updated. Please relaunch your browser. Chrome version: <ph name="TODO_0001">%ls<ex>TODO</ex></ph>, Chrome Frame version: <ph name="TODO_0002">%ls<ex>TODO</ex></ph>
         </message>
         <message name="IDS_VERSIONUNKNOWN">
@@ skipping 324 matching lines @@
         You are viewing a secure Google Chrome page.
       </message>
       <!-- Print Preview -->
       <message name="IDS_PRINT_PREVIEW_NO_PLUGIN" desc="Message to display when the PDF viewer is missing.">
         Google Chrome cannot show the print preview when the built-in PDF viewer is disabled. In order to see the preview, please visit <ph name="BEGIN_LINK">&lt;a target="_blank" rel="noreferrer" href="$1"&gt;</ph>$1<ph name="END_LINK">&lt;/a&gt;</ph>, enable the "Chrome PDF Viewer", and try again.
       </message>
       <message name="IDS_PRINT_PREVIEW_NATIVE_DIALOG" desc="Option offering the user to open the native print dialog, displayed when the PDF viewer is missing.">
         Launch native print dialog
       </message>
 
-      <if expr="os == 'darwin'">
+      <if expr="is_macosx">
         <message name="IDS_APP_MENU_PRODUCT_NAME" desc="The application's short name, used for the Mac's application menu, activity monitor, etc. This should be less than 16 characters. Example: Chrome, not Google Chrome.">
           Chrome
         </message>
         <message name="IDS_HELPER_NAME" desc="The helper application's name.  Should contain the Chrome application name (IDS_PRODUCT_NAME). Example: Google Chrome Helper.">
           Google Chrome Helper
         </message>
         <message name="IDS_SHORT_HELPER_NAME" desc="The helper application's short name, used for the Mac's application menu, activity monitor, etc. Example: Chrome Helper, not Google Chrome Helper.">
           Chrome Helper
         </message>
 
@@ skipping 19 matching lines @@
         <message name="IDS_UTILITY_APP_NAME" desc="The utility application's name.  Should contain the Chrome application name (IDS_PRODUCT_NAME). Example: Google Chrome Utility.">
           Google Chrome Utility
         </message>
         <message name="IDS_SHORT_UTILITY_APP_NAME" desc="The utility application's short name, used for the Mac's application menu, activity monitor, etc. Example: Chrome Utility, not Google Chrome Utility.">
           Chrome Utility
         </message>
       </if>
     </messages>
   </release>
 </grit>