[turbofan] Remove now-dead JSFunctionRef::EnsureHasInitialMap.

R=jarin@chromium.org

Bug: v8:7790
Change-Id: I06ace1a150d7c9a7eff1cd49e7eb38596bf0a188
Reviewed-on: https://chromium-review.googlesource.com/1180895Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55206}

src/compiler/js-heap-broker.cc

@@ -600,16 +600,6 @@ base::Optional<MapRef> HeapObjectRef::TryGetObjectCreateMap() const {
   }
 }
 
-void JSFunctionRef::EnsureHasInitialMap() const {
-  AllowHandleAllocation handle_allocation;
-  AllowHandleDereference allow_handle_dereference;
-  AllowHeapAllocation heap_allocation;
-  // TODO(jarin) Eventually, we will prepare initial maps for resumable
-  // functions (i.e., generators).
-  DCHECK(IsResumableFunction(object<JSFunction>()->shared()->kind()));
-  JSFunction::EnsureHasInitialMap(object<JSFunction>());
-}
-
 base::Optional<MapRef> MapRef::AsElementsKind(ElementsKind kind) const {
   if (broker()->mode() == JSHeapBroker::kDisabled) {
     AllowHandleAllocation handle_allocation;

src/compiler/js-heap-broker.h

@@ -176,7 +176,6 @@ class JSFunctionRef : public JSObjectRef {
   JSGlobalProxyRef global_proxy() const;
   int InitialMapInstanceSizeWithMinSlack() const;
   SharedFunctionInfoRef shared() const;
-  void EnsureHasInitialMap() const;
 };
 
 class JSRegExpRef : public JSObjectRef {