[promises] Clean up promise utils and remove dead code

src/builtins/builtins-promise.h

Index: src/builtins/builtins-promise.h
diff --git a/src/builtins/builtins-promise.h b/src/builtins/builtins-promise.h
index 4a614e46efbc07929c60b53d7848ed91e97d75cc..1b0f98cce6fc1e3f6c17ecbcee43ccbea1096461 100644
--- a/src/builtins/builtins-promise.h
+++ b/src/builtins/builtins-promise.h
@@ -16,6 +16,25 @@ class PromiseBuiltinsAssembler : public CodeStubAssembler {
   explicit PromiseBuiltinsAssembler(CodeAssemblerState* state)
       : CodeStubAssembler(state) {}
 
+  enum PromiseResolvingFunctionContextSlot {

[adamk, 2017/01/13 22:45:08]

Style: These enums should go at the top of the public: section, before even the
constructor.

[gsathya, 2017/01/17 16:36:47]

Done.

+    // Whether the resolve/reject callback was already called.
+    kAlreadyVisitedSlot = Context::MIN_CONTEXT_SLOTS,

[adamk, 2017/01/13 22:45:08]

Please add an #include for contexts.h

[gsathya, 2017/01/17 16:36:47]

Done.

+
+    // 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,
+  };
+
   // These allocate and initialize a promise with pending state and
   // undefined fields.
   //