Fix up intercept and filter notification bar

Per Felipe's suggestion, replaced timer with a flag set on the
msg.target, which is cleared on pageshow events.

lib/ui.js

@@ -176,41 +176,30 @@ function listenOnContentProcessMessages(chromeGlobal) {
   // the content process to ourselves.
   mm.loadFrameScript(data.url('messageBouncer.js'), true);
 
-  let removeNextPluginBar = null;
   mm.addMessageListener('PluginSafety:BrowserEventRelay', (msg) => {
-    if (!msg.data.error && msg.data.type == 'PluginFound' &&
+    if (msg.data.type == 'PluginFound' &&
       msg.data.flashObj.classification.startsWith('ctp-')) {
 
-      // We want to ensure that if no notification bar shows up, we don't clobber
-      // any future legitimate notification bars
-      const clearRemoveNextPluginBarTimeout = 1000;
-
-      // null means that we're okay to set removeNextPluginBar to either true
+      // undefined means that we're okay to set removeNextPluginBar to either true
       // or false. We want to ensure that if any valid ctp- flash objects come
       // through, we clear removeNextPluginBar.
-      if (msg.data.flashObj.path === null && removeNextPluginBar === null) {
-        removeNextPluginBar = true;
-
-        setTimeout(() => {
-          removeNextPluginBar = null;
-        }, clearRemoveNextPluginBarTimeout);
+      if (msg.data.flashObj.path === null && msg.target.removeNextPluginBar === undefined) {
+        msg.target.removeNextPluginBar = true;
       } else if (msg.data.flashObj.path !== null) {
-        removeNextPluginBar = false;
-
-        setTimeout(() => {
-          removeNextPluginBar = null;
-        }, clearRemoveNextPluginBarTimeout);
+        msg.target.removeNextPluginBar = false;
       }
+    } else if (msg.data.type == 'pageshow') {
+      delete msg.target.removeNextPluginBar;
     }
   });
 
   mm.addMessageListener('PluginContent:UpdateHiddenPluginUI', (msg) => {
-    if (removeNextPluginBar) {
-      removeNextPluginBar = null;
-    } else {
+    if (!msg.target.removeNextPluginBar) {
       chromeGlobal.gPluginHandler.updateHiddenPluginUI(msg.target,
         msg.data.haveInsecure, msg.data.actions, msg.principal, msg.data.location);
     }
+
+    delete msg.target.removeNextPluginBar;
   });
 
   mm.addMessageListener('PluginContent:ShowClickToPlayNotification', (msg) => {
@@ -318,15 +307,15 @@ function wireUpWindow(win) {
 
   // Clear gPluginHandler from listening to this, because we're going to
   // intercept it and filter.
-  mm.removeMessageListener('PluginContent:UpdateHiddenPluginUI',
+  chromeGlobal.messageManager.removeMessageListener('PluginContent:UpdateHiddenPluginUI',
     chromeGlobal.gPluginHandler);
 }
 
 function resetWindow(win) {
   const chromeGlobal = viewFor(win);
 
   // Add gPluginHandler back on these messages (see wireUpWindow)
-  mm.removeMessageListener('PluginContent:UpdateHiddenPluginUI',
+  chromeGlobal.messageManager.addMessageListener('PluginContent:UpdateHiddenPluginUI',
     chromeGlobal.gPluginHandler);
 }