Introduce some predicates over variable modes.

src/v8globals.h

Index: src/v8globals.h
diff --git a/src/v8globals.h b/src/v8globals.h
index af1d3aaa1fbf1ba2cae11a3a541a121425f8dc96..38fb02d07a9847fd9d05ddf0ff970da0c1fed9c0 100644
--- a/src/v8globals.h
+++ b/src/v8globals.h
@@ -485,10 +485,10 @@ enum VariableMode {
 
   CONST,           // declared via 'const' declarations
 
-  CONST_HARMONY,   // declared via 'const' declarations in harmony mode
-
   LET,             // declared via 'let' declarations
 
+  CONST_HARMONY,   // declared via 'const' declarations in harmony mode
+
   // Variables introduced by the compiler:
   DYNAMIC,         // always require dynamic lookup (we don't know
                    // the declaration)
@@ -510,6 +510,26 @@ enum VariableMode {
 };
 
 
+inline bool IsDynamicVariableMode(VariableMode mode) {
+  return mode >= DYNAMIC && mode <= DYNAMIC_LOCAL;
+}
+
+
+inline bool IsDeclaredVariableMode(VariableMode mode) {
+  return mode >= VAR && mode <= CONST_HARMONY;
+}
+
+
+inline bool IsLexicalVariableMode(VariableMode mode) {
+  return mode >= LET && mode <= CONST_HARMONY;
+}
+
+
+inline bool IsImmutableVariableMode(VariableMode mode) {
+  return mode == CONST || mode == CONST_HARMONY;
+}
+
+
 // ES6 Draft Rev3 10.2 specifies declarative environment records with mutable
 // and immutable bindings that can be in two states: initialized and
 // uninitialized. In ES5 only immutable bindings have these two states. When