Use a placeholder instead of the default plugin for missing plug-ins on Mac and Linux.

chrome/app/generated_resources.grd

 <?xml version="1.0" encoding="UTF-8"?>
 
 <!--
 This file contains definitions of resources that will be translated for each
 locale.  The variables is_win, is_macosx, is_linux, and is_posix are available
 for making strings OS specific.  Other platform defines such as use_titlecase
 are declared in build/common.gypi.
 -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
@@ skipping 4704 matching lines @@
       </message>
       <message name="IDS_PLUGIN_BLOCKED" desc="The placeholder text for a blocked disabled plug-in.">
         The <ph name="PLUGIN_NAME">$1<ex>Flash</ex></ph> plug-in is not allowed.
       </message>
       <message name="IDS_PLUGIN_OUTDATED" desc="The placeholder text for an outdated disabled plug-in.">
         The <ph name="PLUGIN_NAME">$1<ex>Flash</ex></ph> plug-in is out of date.
       </message>
       <message name="IDS_PLUGIN_NOT_AUTHORIZED" desc="The placeholder text for a plug-in that requires user permission to run.">
         The <ph name="PLUGIN_NAME">$1<ex>Java</ex></ph> plug-in needs your permission to run.
       </message>
+      <message name="IDS_PLUGIN_NOT_FOUND" desc="The placeholder text for a plug-in that is not installed.">
+        No plug-in available to display this content.
+      </message>
 
       <!-- Session Crashed Info Bar-->
       <message name="IDS_SESSION_CRASHED_VIEW_RESTORE_BUTTON" desc="Title of the restore button in the session crashed view.">
         Restore
       </message>
 
       <!-- Bad Flags Info Bar-->
       <message name="IDS_BAD_FLAGS_WARNING_MESSAGE" desc="Message shown when an unsupported command-line flag is used. [Keep it short so it fits in the infobar.]">
         You are using an unsupported command-line flag: <ph name="BAD_FLAG">$1<ex>--no-sandbox</ex></ph>. Stability and security will suffer.
       </message>
@@ skipping 9014 matching lines @@
     </messages>
     <structures fallback_to_english="true">
       <!-- Make sure these stay in sync with the structures in generated_resources.grd. -->
       <structure name="IDD_CHROME_FRAME_FIND_DIALOG" file="cf_resources.rc" type="dialog" >
       </structure>
       <structure name="IDD_CHROME_FRAME_READY_PROMPT" file="cf_resources.rc" type="dialog" >
       </structure>
     </structures>
   </release>
 </grit>