Introduce some predicates over variable modes.

src/arm/full-codegen-arm.cc

Index: src/arm/full-codegen-arm.cc
diff --git a/src/arm/full-codegen-arm.cc b/src/arm/full-codegen-arm.cc
index a26c596051f8b92d2e2230d13e28d3c126f7d554..85e94f29649dacf999f1fbf7afd4415a6f48bfb0 100644
--- a/src/arm/full-codegen-arm.cc
+++ b/src/arm/full-codegen-arm.cc
@@ -832,10 +832,9 @@ void FullCodeGenerator::VisitVariableDeclaration(
       Comment cmnt(masm_, "[ VariableDeclaration");
       __ mov(r2, Operand(variable->name()));
       // Declaration 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;
       __ mov(r1, Operand(Smi::FromInt(attr)));
       // Push initial value, if any.
       // Note: For variables we must not push an initial value (such as