Update MissingPlugin for Firefox 15

Review by: acleung@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@11254 8db76d5a-ed1c-0410-87a9-c151d255dfc7
diff --git a/MissingPlugin/war/MissingPlugin.html b/MissingPlugin/war/MissingPlugin.html
index 46ccb3e..eb709ae 100644
--- a/MissingPlugin/war/MissingPlugin.html
+++ b/MissingPlugin/war/MissingPlugin.html
@@ -35,7 +35,7 @@
 
           "firefox-old" :
           {
-            "caption" : "Sorry, the GWT Developer Plugin only supports Firefox 3.0 - 10.0 at present",
+            "caption" : "Sorry, the GWT Developer Plugin only supports Firefox 3.0 - 15.0 at present",
             "url" : "http://www.getfirefox.com",
             "supported" : false
           },
@@ -171,17 +171,15 @@
       } else if (ua.indexOf("opera") != -1) {
         id = 'opera';
       } else if (ua.indexOf("gecko") != -1) {
-      if (ua.indexOf("rv:1.9") != -1 ||
-          ua.indexOf("rv:2.0") != -1 ||
-          ua.indexOf("rv:5.0") != -1 ||
-          ua.indexOf("rv:6.0") != -1 ||
-          ua.indexOf("rv:7.0") != -1 ||
-          ua.indexOf("rv:8.0") != -1 ||
-          ua.indexOf("rv:9.0") != -1 ||
-          ua.indexOf("rv:10.0") != -1) {
-          id = 'firefox';
-        } else {
-          id = 'firefox-old';
+        // Note: Gecko version != Firefox version before 5.0.
+        // See: https://developer.mozilla.org/en-US/docs/Gecko_user_agent_string_reference
+        var gecko_versions = ["1.9", "2.0", "5.0", "6.0", "7.0", "8.0", "9.0", "10.0", "11.0", "12.0", "13.0", "14.0", "15.0"];
+        id = 'firefox-old';
+        for (var i = 0; i < gecko_versions.length; i++) {
+          if (ua.indexOf("rv:" + gecko_versions[i]) != -1) {
+            id = 'firefox';
+            break;
+          }
         }
       }
       downloadInfo.inferredDownloadId = id;
@@ -193,7 +191,7 @@
   <noscript>
     <div style="width: 22em; position: absolute; left: 50%; margin-left: -11em; color: red; background-color: white; border: 1px solid red; padding: 4px; font-family: sans-serif">
       The Google Web Toolkit Developer Plugin does not appear to be installed.
-      However, you also don't seem to have a browser that is willing to run JavaScript.
+      Also, you also don't seem to have a browser that is willing to run JavaScript.
       Please enable JavaScript or switch to a browser that supports JavaScript and try again.
     </div>
   </noscript>