Implement delete trap for proxies.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 9765fe2a0ab242f897145ea7d763ea21a8616b27..00267595c2f3850587fbf8bf4ca25caeb65b013f 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1359,6 +1359,12 @@ class HeapNumber: public HeapObject {
 // JSObject and JSProxy.
 class JSReceiver: public HeapObject {
  public:
+  enum DeleteMode {
+    NORMAL_DELETION,
+    STRICT_DELETION,
+    FORCE_DELETION
+  };
+
   // Casting.
   static inline JSReceiver* cast(Object* obj);
 
@@ -1373,6 +1379,8 @@ class JSReceiver: public HeapObject {
                                            PropertyAttributes attributes,
                                            StrictModeFlag strict_mode);
 
+  MUST_USE_RESULT MaybeObject* DeleteProperty(String* name, DeleteMode mode);
+
   // Returns the class name ([[Class]] property in the specification).
   String* class_name();
 
@@ -1422,12 +1430,6 @@ class JSReceiver: public HeapObject {
 // caching.
 class JSObject: public JSReceiver {
  public:
-  enum DeleteMode {
-    NORMAL_DELETION,
-    STRICT_DELETION,
-    FORCE_DELETION
-  };
-
   enum ElementsKind {
     // The "fast" kind for tagged values. Must be first to make it possible
     // to efficiently check maps if they have fast elements.
@@ -6491,14 +6493,18 @@ class JSProxy: public JSReceiver {
   static inline JSProxy* cast(Object* obj);
 
   MUST_USE_RESULT MaybeObject* SetPropertyWithHandler(
-      String* name_raw,
-      Object* value_raw,
+      String* name,
+      Object* value,
       PropertyAttributes attributes,
       StrictModeFlag strict_mode);
 
+  MUST_USE_RESULT MaybeObject* DeletePropertyWithHandler(
+      String* name,
+      DeleteMode mode);
+
   MUST_USE_RESULT PropertyAttributes GetPropertyAttributeWithHandler(
       JSReceiver* receiver,
-      String* name_raw,
+      String* name,
       bool* has_exception);
 
   // Dispatched behavior.