[proxies] Add all-can-read/String/Symbol filtering support to GetKeys()

src/key-accumulator.cc

Index: src/key-accumulator.cc
diff --git a/src/key-accumulator.cc b/src/key-accumulator.cc
index f79561b392ba51b1a77534d539780b3729f6fa7b..468a1f5f28f3fdb47e2af8a41838f5ea8f9ce7c6 100644
--- a/src/key-accumulator.cc
+++ b/src/key-accumulator.cc
@@ -103,6 +103,7 @@ bool KeyAccumulator::AddKey(Handle<Object> key, AddKeyConversion convert) {
     if (Handle<Symbol>::cast(key)->is_private()) return false;
     return AddSymbolKey(key);
   }
+  if (filter_ & SKIP_STRINGS) return false;
   // Make sure we do not add keys to a proxy-level (see AddKeysFromProxy).
   DCHECK_LE(0, level_string_length_);
   // In some cases (e.g. proxies) we might get in String-converted ints which
@@ -235,6 +236,7 @@ MaybeHandle<FixedArray> FilterProxyKeys(Isolate* isolate, Handle<JSProxy> owner,
         continue;  // Skip this key.
       }
     }
+    if (filter & SKIP_STRINGS) continue;  // Skip this key.
     if (filter & ONLY_ENUMERABLE) {
       PropertyDescriptor desc;
       bool found =