Issue 5098 - Expose FilterStorage initialization state

test/filterStorage_readwrite.js

Index: test/filterStorage_readwrite.js
===================================================================
--- a/test/filterStorage_readwrite.js
+++ b/test/filterStorage_readwrite.js
@@ -105,22 +105,25 @@ function canonize(data)
   });
   return sections.map(
     section => [section.header].concat(section.data).join("\n")
   ).join("\n");
 }
 
 function testReadWrite(test, withExternal)
 {
+  test.ok(!FilterStorage.initialized, "Uninitialized before the first load");
+
   return testData.then(data =>
   {
     dataFile.contents = data;
     return loadFilters();
   }).then(() =>
   {
+    test.ok(FilterStorage.initialized, "Initialize after the first load");
     test.equal(FilterStorage.fileProperties.version, FilterStorage.formatVersion, "File format version");
 
     if (withExternal)
     {
       {
         let subscription = new ExternalSubscription("~external~external subscription ID", "External subscription");
         subscription.filters = [Filter.fromText("foo"), Filter.fromText("bar")];
         FilterStorage.addSubscription(subscription);