Revert "Avoid setting up binding & calling GetNavigationSourceId more than once."

This reverts commit 0cfa7036.

Reason for revert:
Instrumentation no longer needed. It was meant only for 1 milestone.

Original change's description:
> Avoid setting up binding & calling GetNavigationSourceId more than once.
>
> Change-Id: If368dc7696a04992bac3a95489954f9e97435894
>
> BUG: 1018156,1036721,1036720
> Change-Id: If368dc7696a04992bac3a95489954f9e97435894
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1980665
> Auto-Submit: Bartek Nowierski <bartekn@chromium.org>
> Reviewed-by: Yuta Kitamura <yutak@chromium.org>
> Commit-Queue: Bartek Nowierski <bartekn@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#727347}

TBR=yutak@chromium.org,haraken@chromium.org,bartekn@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: I2aeee271002ea2a594950c664ba03b5bf01f68b8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1982333
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#727446}

third_party/blink/renderer/core/dom/document.cc

@@ -4133,9 +4133,7 @@ bool Document::CheckCompletedInternal() {
       return false;
   }
 
-  // !ukm_binding_ is checked to avoid repeating work.
-  if (frame_ && frame_->Client()->GetRemoteNavigationAssociatedInterfaces() &&
-      !ukm_binding_) {
+  if (frame_ && frame_->Client()->GetRemoteNavigationAssociatedInterfaces()) {
     ukm_binding_ = std::make_unique<
         mojo::AssociatedRemote<mojom::blink::UkmSourceIdFrameHost>>();
     frame_->Client()->GetRemoteNavigationAssociatedInterfaces()->GetInterface(