Remove unimplemented CreateCSP function.

TBR=yhirano@chromium.org

Bug: None
Change-Id: Ib4ef9bb1903d6cf54b65f909f7b242c5bdbe8cec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2110024Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Auto-Submit: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#752034}

third_party/blink/renderer/core/loader/document_loader.h

@@ -370,9 +370,6 @@ class CORE_EXPORT DocumentLoader : public GarbageCollected<DocumentLoader>,
   // opaque origin.
   void ReplaceWithEmptyDocument();
 
-  ContentSecurityPolicy* CreateCSP(
-      const ResourceResponse&,
-      const base::Optional<WebOriginPolicy>& origin_policy);
   DocumentPolicy::ParsedDocumentPolicy CreateDocumentPolicy();
 
   void StartLoadingInternal();