Fix notification centre icons and dismissal

shell/plugins/notification-center/HistoryModel.js

@@ -1,18 +1,23 @@
 .pragma library
 
-// Each history file is one line of JSON, so the reader concatenates the
-// directory and parses line by line. Newest first, by timestamp.
+// Each history file is one line of JSON, and the reader prefixes every line
+// with the file's name and a tab so an entry can be removed later. Newest
+// first, by timestamp.
 function parseHistory(raw) {
   var lines = String(raw || "").split("\n")
   var entries = []
   for (var i = 0; i < lines.length; i++) {
     var line = lines[i].trim()
     if (!line) continue
+    var tab = line.indexOf("\t")
+    var fileName = tab >= 0 ? line.slice(0, tab) : ""
+    var json = tab >= 0 ? line.slice(tab + 1) : line
     try {
-      var value = JSON.parse(line)
+      var value = JSON.parse(json)
       if (!value || typeof value !== "object") continue
       entries.push({
         id: value.id || 0,
+        fileName: fileName,
         app: value.app || "",
         summary: value.summary || "",
         body: value.body || "",