WebUI: Add JavaScript lifecycle-control to WebUIMessageHandler.

chrome/browser/ui/webui/md_downloads/md_downloads_dom_handler.cc

Index: chrome/browser/ui/webui/md_downloads/md_downloads_dom_handler.cc
diff --git a/chrome/browser/ui/webui/md_downloads/md_downloads_dom_handler.cc b/chrome/browser/ui/webui/md_downloads/md_downloads_dom_handler.cc
index b6ddf97828beda84ea7fb6fcb2b08d34afad29e7..c2018934f2564d1ca2196fa8d955f26b12c8eb91 100644
--- a/chrome/browser/ui/webui/md_downloads/md_downloads_dom_handler.cc
+++ b/chrome/browser/ui/webui/md_downloads/md_downloads_dom_handler.cc
@@ -133,7 +133,11 @@ void MdDownloadsDOMHandler::RegisterMessages() {
                  weak_ptr_factory_.GetWeakPtr()));
 }
 
-void MdDownloadsDOMHandler::RenderViewReused() {
+void MdDownloadsDOMHandler::OnJavascriptAllowed() {
+  list_tracker_.StartAndSendChunk();
+}
+
+void MdDownloadsDOMHandler::OnJavascriptDisallowed() {
   list_tracker_.Stop();
   list_tracker_.Reset();
   CheckForRemovedFiles();

[Dan Beam, 2016/04/18 23:13:20]

technically we want to check for removed files on *refresh*.

what are the chances that refresh and disallowing javascript diverge eventually?

[tommycli, 2016/04/19 17:45:37]

Hmm... I would imagine OnJavascriptDisallowed to being a superset of
OnRenderViewReused.

A Refresh should ALWAYS trigger a OnJavascriptDisallowed. Additionally, a
'Polymer element detached' should probably also trigger a DisallowJavascript
(currently non-existent) call.

@@ -146,7 +150,7 @@ void MdDownloadsDOMHandler::HandleGetDownloads(const base::ListValue* args) {
   if (terms_changed)
     list_tracker_.Reset();
 
-  list_tracker_.StartAndSendChunk();
+  AllowJavascript();
 }
 
 void MdDownloadsDOMHandler::HandleOpenFile(const base::ListValue* args) {