[Arguments] Mark functions with duplicated parameters.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 26edf212f1acd9ed97471b8d84b02a4738089fd7..223c369a101b82ed677b7638a15ed97ea034c247 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4309,6 +4309,9 @@ class SharedFunctionInfo: public HeapObject {
   // False if the function definitely does not allocate an arguments object.
   DECL_BOOLEAN_ACCESSORS(uses_arguments)
 
+  // True if the function has any duplicated parameter names.
+  DECL_BOOLEAN_ACCESSORS(has_duplicate_parameters)
+
   // Indicates whether or not the code in the shared function support
   // deoptimization.
   inline bool has_deoptimization_support();
@@ -4482,14 +4485,19 @@ class SharedFunctionInfo: public HeapObject {
   static const int kStartPositionMask = ~((1 << kStartPositionShift) - 1);
 
   // Bit positions in compiler_hints.
-  static const int kHasOnlySimpleThisPropertyAssignments = 0;
-  static const int kAllowLazyCompilation = 1;
-  static const int kLiveObjectsMayExist = 2;
-  static const int kCodeAgeShift = 3;
-  static const int kCodeAgeMask = 0x7;
-  static const int kOptimizationDisabled = 6;
-  static const int kStrictModeFunction = 7;
-  static const int kUsesArguments = 8;
+  static const int kCodeAgeSize = 3;
+  static const int kCodeAgeMask = (1 << kCodeAgeSize) - 1;
+
+  enum CompilerHints {
+    kHasOnlySimpleThisPropertyAssignments,
+    kAllowLazyCompilation,
+    kLiveObjectsMayExist,
+    kCodeAgeShift,
+    kOptimizationDisabled = kCodeAgeShift + kCodeAgeSize,
+    kStrictModeFunction,
+    kUsesArguments,
+    kHasDuplicateParameters
+  };
 
  private:
 #if V8_HOST_ARCH_32_BIT