[turbofan] Remove obsolete BuildLoadBuiltinsObject.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/1305163008

Cr-Commit-Position: refs/heads/master@{#30417}

src/compiler/ast-graph-builder.cc

@@ -3737,14 +3737,6 @@ Node* AstGraphBuilder::BuildLoadImmutableObjectField(Node* object, int offset) {
 }
 
 
-Node* AstGraphBuilder::BuildLoadBuiltinsObject() {
-  Node* global = BuildLoadGlobalObject();
-  Node* builtins =
-      BuildLoadObjectField(global, JSGlobalObject::kBuiltinsOffset);
-  return builtins;
-}
-
-
 Node* AstGraphBuilder::BuildLoadGlobalObject() {
   const Operator* load_op =
       javascript()->LoadContext(0, Context::GLOBAL_OBJECT_INDEX, true);

src/compiler/ast-graph-builder.h

@@ -315,7 +315,6 @@ class AstGraphBuilder : public AstVisitor {
                          TypeFeedbackId id, int slot_index);
 
   // Builders for accessing the function context.
-  Node* BuildLoadBuiltinsObject();
   Node* BuildLoadGlobalObject();
   Node* BuildLoadNativeContextField(int index);
   Node* BuildLoadGlobalProxy();