Deprecate non-standard Array methods and clarify Object::isArray

BUG=none
R=neis@chromium.org
LOG=y

Review URL: https://codereview.chromium.org/1493053004

Cr-Commit-Position: refs/heads/master@{#32551}

include/v8.h

@@ -1736,7 +1736,8 @@ class V8_EXPORT Value : public Data {
   bool IsFunction() const;
 
   /**
-   * Returns true if this value is an array.
+   * Returns true if this value is an array. Note that it will return false for
+   * an Proxy for an array.
    */
   bool IsArray() const;
 
@@ -2995,10 +2996,11 @@ class V8_EXPORT Array : public Object {
    * Clones an element at index |index|.  Returns an empty
    * handle if cloning fails (for any reason).
    */
-  V8_DEPRECATE_SOON("Use maybe version",
-                    Local<Object> CloneElementAt(uint32_t index));
-  V8_WARN_UNUSED_RESULT MaybeLocal<Object> CloneElementAt(
-      Local<Context> context, uint32_t index);
+  V8_DEPRECATED("Cloning is not supported.",
+                Local<Object> CloneElementAt(uint32_t index));
+  V8_DEPRECATED("Cloning is not supported.",
+                MaybeLocal<Object> CloneElementAt(Local<Context> context,
+                                                  uint32_t index));
 
   /**
    * Creates a JavaScript array with the given length. If the length

src/api.cc

@@ -6204,10 +6204,7 @@ MaybeLocal<Object> Array::CloneElementAt(Local<Context> context,
 }
 
 
-Local<Object> Array::CloneElementAt(uint32_t index) {
-  auto context = ContextFromHeapObject(Utils::OpenHandle(this));
-  RETURN_TO_LOCAL_UNCHECKED(CloneElementAt(context, index), Object);
-}
+Local<Object> Array::CloneElementAt(uint32_t index) { return Local<Object>(); }
 
 
 Local<v8::Map> v8::Map::New(Isolate* isolate) {