Merge in remaining header elements (eg: link icons, manifest, meta an…

…d title) (#752)

* Update page_renderer.ts

* Spacing change to re-trigger CI

* Lint updates

src/core/drive/page_renderer.ts

@@ -60,10 +60,10 @@ export class PageRenderer extends Renderer<HTMLBodyElement, PageSnapshot> {
   }
 
   async mergeHead() {
+    const mergedHeadElements = this.mergeProvisionalElements()
     const newStylesheetElements = this.copyNewHeadStylesheetElements()
     this.copyNewHeadScriptElements()
-    this.removeCurrentHeadProvisionalElements()
-    this.copyNewHeadProvisionalElements()
+    await mergedHeadElements
     await newStylesheetElements
   }
 
@@ -96,6 +96,43 @@ export class PageRenderer extends Renderer<HTMLBodyElement, PageSnapshot> {
     }
   }
 
+  async mergeProvisionalElements() {
+    const newHeadElements = [...this.newHeadProvisionalElements]
+
+    for (const element of this.currentHeadProvisionalElements) {
+      if (!this.isCurrentElementInElementList(element, newHeadElements)) {
+        document.head.removeChild(element)
+      }
+    }
+
+    for (const element of newHeadElements) {
+      document.head.appendChild(element)
+    }
+  }
+
+  isCurrentElementInElementList(element: Element, elementList: Element[]) {
+    for (const [index, newElement] of elementList.entries()) {
+      // if title element...
+      if (element.tagName == "TITLE") {
+        if (newElement.tagName != "TITLE") {
+          continue
+        }
+        if (element.innerHTML == newElement.innerHTML) {
+          elementList.splice(index, 1)
+          return true
+        }
+      }
+
+      // if any other element...
+      if (newElement.isEqualNode(element)) {
+        elementList.splice(index, 1)
+        return true
+      }
+    }
+
+    return false
+  }
+
   removeCurrentHeadProvisionalElements() {
     for (const element of this.currentHeadProvisionalElements) {
       document.head.removeChild(element)