Introduce some predicates over variable modes.

src/ia32/full-codegen-ia32.cc

Index: src/ia32/full-codegen-ia32.cc
diff --git a/src/ia32/full-codegen-ia32.cc b/src/ia32/full-codegen-ia32.cc
index 64400de81d1f1eeca8f8c950b53a5b60ab17c9b4..de8e490d2873c87cc4c43c46b7326eafcb0411fb 100644
--- a/src/ia32/full-codegen-ia32.cc
+++ b/src/ia32/full-codegen-ia32.cc
@@ -810,10 +810,9 @@ void FullCodeGenerator::VisitVariableDeclaration(
       __ push(esi);
       __ push(Immediate(variable->name()));
       // VariableDeclaration nodes are always introduced in one of four modes.
-      ASSERT(mode == VAR || mode == LET ||
-             mode == CONST || mode == CONST_HARMONY);
-      PropertyAttributes attr = (mode == CONST || mode == CONST_HARMONY)
-          ? READ_ONLY : NONE;
+      ASSERT(IsDeclaredVariableMode(mode));
+      PropertyAttributes attr =
+          IsImmutableVariableMode(mode) ? READ_ONLY : NONE;
       __ push(Immediate(Smi::FromInt(attr)));
       // Push initial value, if any.
       // Note: For variables we must not push an initial value (such as