WebUI: Add JavaScript lifecycle-control to WebUIMessageHandler.

content/browser/webui/web_ui_message_handler.cc

Index: content/browser/webui/web_ui_message_handler.cc
diff --git a/content/browser/webui/web_ui_message_handler.cc b/content/browser/webui/web_ui_message_handler.cc
index 44f065d44ed6f90d94387cd2af0e9ffdbb029779..4daf294d7f0ba30b6e6c72da37aa9c36763f3480 100644
--- a/content/browser/webui/web_ui_message_handler.cc
+++ b/content/browser/webui/web_ui_message_handler.cc
@@ -11,6 +11,14 @@
 
 namespace content {
 
+void WebUIMessageHandler::AllowJavascript() {
+  if (javascript_allowed_)
+    return;
+

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

we should be checking this was called validly here as well, i.e.

CHECK(web_ui());
CHECK(web_ui()->SomeNewMethodThatChecksIfWeCanExecuteJavascript());

[tommycli, 2016/04/19 17:45:38]

Done.

+  javascript_allowed_ = true;
+  OnJavascriptAllowed();
+}
+
 bool WebUIMessageHandler::ExtractIntegerValue(const base::ListValue* value,
                                               int* out_int) {
   std::string string_value;
@@ -45,4 +53,12 @@ base::string16 WebUIMessageHandler::ExtractStringValue(
   return base::string16();
 }
 
+void WebUIMessageHandler::RenderViewReused() {
+  if (!javascript_allowed_)
+    return;
+
+  javascript_allowed_ = false;
+  OnJavascriptDisallowed();
+}
+
 }  // namespace content