[es6] Introduce %ToInteger and %ToLength.

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index 03ec3a809545df0755d6df0a9811a1b0723dd7ba..9d4bafb6ffdc152c511fc4ce0e9d49db1d5f55f6 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -774,6 +774,10 @@ const uint64_t kHoleNanInt64 =
     (static_cast<uint64_t>(kHoleNanUpper32) << 32) | kHoleNanLower32;
 
 
+// ES6 section 20.1.2.6 Number.MAX_SAFE_INTEGER
+const double kMaxSafeInteger = 9007199254740991.0;  // 2^53-1
+
+
 // The order of this enum has to be kept in sync with the predicates below.
 enum VariableMode {
   // User declared variables: