creative comment injection spot reverted:

- reverted injection point of creative comment to pre-PR 6860
- added code to reinject comment in case it was removed upon rendering

(cherry picked from commit 7c21d26)

src/prebid.js

@@ -403,10 +403,23 @@ function emitAdRenderSucceeded({ doc, bid, id }) {
   events.emit(AD_RENDER_SUCCEEDED, data);
 }
 
+/**
+ * This function will check for presence of given node in given parent. If not present - will inject it.
+ * @param {Node} node node, whose existance is in question
+ * @param {Document} doc document element do look in
+ * @param {string} tagName tag name to look in
+ */
+function reinjectNodeIfRemoved(node, doc, tagName) {
+  const injectionNode = doc.querySelector(tagName);
+  if (!node.parentNode || node.parentNode !== injectionNode) {
+    insertElement(node, doc, tagName);
+  }
+}
+
 /**
  * This function will render the ad (based on params) in the given iframe document passed through.
  * Note that doc SHOULD NOT be the parent document page as we can't doc.write() asynchronously
- * @param  {HTMLDocument} doc document
+ * @param  {Document} doc document
  * @param  {string} id bid id to locate the ad
  * @alias module:pbjs.renderAd
  */
@@ -450,10 +463,11 @@ $$PREBID_GLOBAL$$.renderAd = hook('async', function (doc, id, options) {
           const {height, width, ad, mediaType, adUrl, renderer} = bid;
 
           const creativeComment = document.createComment(`Creative ${bid.creativeId} served by ${bid.bidder} Prebid.js Header Bidding`);
+          insertElement(creativeComment, doc, 'html');
 
           if (isRendererRequired(renderer)) {
             executeRenderer(renderer, bid);
-            insertElement(creativeComment, doc, 'html');
+            reinjectNodeIfRemoved(creativeComment, doc, 'html');
             emitAdRenderSucceeded({ doc, bid, id });
           } else if ((doc === document && !inIframe()) || mediaType === 'video') {
             const message = `Error trying to write ad. Ad render call ad id ${id} was prevented from writing to the main document.`;
@@ -472,7 +486,7 @@ $$PREBID_GLOBAL$$.renderAd = hook('async', function (doc, id, options) {
             doc.write(ad);
             doc.close();
             setRenderSize(doc, width, height);
-            insertElement(creativeComment, doc, 'html');
+            reinjectNodeIfRemoved(creativeComment, doc, 'html');
             callBurl(bid);
             emitAdRenderSucceeded({ doc, bid, id });
           } else if (adUrl) {
@@ -485,7 +499,7 @@ $$PREBID_GLOBAL$$.renderAd = hook('async', function (doc, id, options) {
 
             insertElement(iframe, doc, 'body');
             setRenderSize(doc, width, height);
-            insertElement(creativeComment, doc, 'html');
+            reinjectNodeIfRemoved(creativeComment, doc, 'html');
             callBurl(bid);
             emitAdRenderSucceeded({ doc, bid, id });
           } else {

test/spec/unit/pbjs_api_spec.js

@@ -1135,13 +1135,15 @@ describe('Unit: Prebid Module', function () {
             height: 0
           }
         },
-        getElementsByTagName: sinon.stub()
+        getElementsByTagName: sinon.stub(),
+        querySelector: sinon.stub()
       };
 
       elStub = {
         insertBefore: sinon.stub()
       };
       doc.getElementsByTagName.returns([elStub]);
+      doc.querySelector.returns(elStub);
 
       spyLogError = sinon.spy(utils, 'logError');
       spyLogMessage = sinon.spy(utils, 'logMessage');