Added documentation.

Minor change to filtering tabs.
Implicitly use the error parameter.

Client/Frontend/Browser/ResourceDownloadManager.swift

@@ -48,7 +48,7 @@ class ResourceDownloadManager: TabContentScript {
         do {
             let response = try DownloadedResourceResponse.from(message: message)
             tab?.temporaryDocument?.onDocumentDownloaded(document: response, error: nil)
-        } catch let error {
+        } catch {
             tab?.temporaryDocument?.onDocumentDownloaded(document: nil, error: error)
         }
     }

Client/Frontend/Browser/TabManager.swift

@@ -530,7 +530,7 @@ class TabManager: NSObject {
         if tab.isPrivate {
             // Only when ALL tabs are dead, we clean up.
             // This is because other tabs share the same data-store.
-            if allTabs.filter({ $0.isPrivate }).count <= 1 {
+            if tabsForCurrentMode.count <= 1 {
                 removeAllBrowsingDataForTab(tab)
             }
         }

Client/Frontend/Browser/UserScriptManager.swift

@@ -126,6 +126,10 @@ class UserScriptManager {
             return nil
         }
         var alteredSource: String = source
+
+        //Verify that the application itself is making a call to the JS script instead of other scripts on the page.
+        //This variable will be unique amongst scripts loaded in the page.
+        //When the script is called, the token is provided in order to access teh script variable.
         let token = UserScriptManager.securityToken.uuidString.replacingOccurrences(of: "-", with: "", options: .literal)
         alteredSource = alteredSource.replacingOccurrences(of: "$<downloadManager>", with: "D\(token)", options: .literal)