[promises] Clean up promise utils and remove dead code

src/builtins/builtins-promise.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/code-stub-assembler.h"
+#include "src/contexts.h"
 
 namespace v8 {
 namespace internal {
 
 typedef compiler::Node Node;
 typedef CodeStubAssembler::ParameterMode ParameterMode;
 typedef compiler::CodeAssemblerState CodeAssemblerState;
 
 class PromiseBuiltinsAssembler : public CodeStubAssembler {
  public:
+  enum PromiseResolvingFunctionContextSlot {
+    // Whether the resolve/reject callback was already called.
+    kAlreadyVisitedSlot = Context::MIN_CONTEXT_SLOTS,
+
+    // The promise which resolve/reject callbacks fulfill.
+    kPromiseSlot,
+
+    // Whether to trigger a debug event or not. Used in catch
+    // prediction.
+    kDebugEventSlot,
+    kPromiseContextLength,
+  };
+
+  enum FunctionContextSlot {
+    kCapabilitySlot = Context::MIN_CONTEXT_SLOTS,
+
+    kCapabilitiesContextLength,
+  };
+
   explicit PromiseBuiltinsAssembler(CodeAssemblerState* state)
       : CodeStubAssembler(state) {}
-
   // These allocate and initialize a promise with pending state and
   // undefined fields.
   //
   // This uses undefined as the parent promise for the promise init
   // hook.
   Node* AllocateAndInitJSPromise(Node* context);
   // This uses the given parent as the parent promise for the promise
   // init hook.
   Node* AllocateAndInitJSPromise(Node* context, Node* parent);
 
@@ skipping 63 matching lines @@
                              bool debug_event);
   void InternalPromiseReject(Node* context, Node* promise, Node* value,
                              Node* debug_event);
 
  private:
   Node* AllocateJSPromise(Node* context);
 };
 
 }  // namespace internal
 }  // namespace v8