[Pale-Moon] Issue #1744 - Add pref to ask for master password on application start.

This is a solution for some users having issues with multiple MP prompts due to
either a race or asynchronously-triggered features that each need password
database access (e.g. website login + sync)

Based on Interlink's similar solution by Matt A. Tobin

application/palemoon/components/nsBrowserGlue.js

@@ -286,6 +286,7 @@ BrowserGlue.prototype = {
         break;
       case "profile-after-change":
          this._onProfileAfterChange();
+         this._promptForMasterPassword();
          break;
       case "browser-search-engine-modified":
         if (data != "engine-default" && data != "engine-current") {
@@ -409,6 +410,26 @@ BrowserGlue.prototype = {
   {
     this._copyDefaultProfileFiles();
   },
+  
+  _promptForMasterPassword: function() {
+    if (!Services.prefs.getBoolPref("signon.startup.prompt", false))
+      return;
+
+    // Try to avoid the multiple master password prompts on startup scenario
+    // by prompting for the master password upfront.
+    let token = Components.classes["@mozilla.org/security/pk11tokendb;1"]
+                          .getService(Components.interfaces.nsIPK11TokenDB)
+                          .getInternalKeyToken();
+
+    // Only log in to the internal token if it is already initialized,
+    // otherwise we get a "Change Master Password" dialog.
+    try {
+      if (!token.needsUserInit)
+        token.login(false);
+    } catch (ex) {
+      // If user cancels an exception is expected.
+    }
+  },
 
   _onAppDefaults: function() {
     // apply distribution customizations (prefs)