Bug 1306124 - Consistently emit the last rendered message in dom for jsterm.execute and with new-messages event;r=linclark

MozReview-Commit-ID: 5100HMmdTr2

devtools/client/webconsole/new-console-output/new-console-output-wrapper.js

@@ -17,6 +17,7 @@ const FilterBar = React.createFactory(require("devtools/client/webconsole/new-co
 const store = configureStore();
 
 function NewConsoleOutputWrapper(parentNode, jsterm, toolbox, owner) {
+  this.parentNode = parentNode;
   this.parentNode = parentNode;
   this.jsterm = jsterm;
   this.toolbox = toolbox;
@@ -68,6 +69,12 @@ NewConsoleOutputWrapper.prototype = {
   dispatchMessagesClear: () => {
     store.dispatch(actions.messagesClear());
   },
+  getLastMessage: function() {
+    // Return the last message in the DOM as the message that was just dispatched. This may not
+    // always be correct in the case of filtered messages, but it's close enough for our tests.
+    let messageNodes = this.parentNode.querySelectorAll(".message");
+    return messageNodes[messageNodes.length - 1]
+  },
 };
 
 // Exports from this module