Add interceptor support for symbols

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 80442b4608673f7a470a175d7bde310ebd1bec29..6b0621e452ac7811bb72d46c55b0ef99494ef36f 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -10844,6 +10844,12 @@ class InterceptorInfo: public Struct {
   DECL_ACCESSORS(deleter, Object)
   DECL_ACCESSORS(enumerator, Object)
   DECL_ACCESSORS(data, Object)
+  DECL_BOOLEAN_ACCESSORS(can_intercept_symbols)
+
+  // TODO(wingo): Remove flags field once all interceptors can intercept
+  // symbols.
+  inline int flags() const;
+  inline void set_flags(int flags);
 
   DECLARE_CAST(InterceptorInfo)
 
@@ -10857,7 +10863,10 @@ class InterceptorInfo: public Struct {
   static const int kDeleterOffset = kQueryOffset + kPointerSize;
   static const int kEnumeratorOffset = kDeleterOffset + kPointerSize;
   static const int kDataOffset = kEnumeratorOffset + kPointerSize;
-  static const int kSize = kDataOffset + kPointerSize;
+  static const int kFlagsOffset = kDataOffset + kPointerSize;
+  static const int kSize = kFlagsOffset + kPointerSize;
+
+  static const int kCanInterceptSymbolsBit = 0;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(InterceptorInfo);