Introduce some predicates over variable modes.

src/mips/full-codegen-mips.cc

Index: src/mips/full-codegen-mips.cc
diff --git a/src/mips/full-codegen-mips.cc b/src/mips/full-codegen-mips.cc
index b78c78332eb5370df91969b841df1dfd18eb45ed..d691a1230894e074a140a53f53d8d58453160a78 100644
--- a/src/mips/full-codegen-mips.cc
+++ b/src/mips/full-codegen-mips.cc
@@ -849,10 +849,9 @@ void FullCodeGenerator::VisitVariableDeclaration(
       Comment cmnt(masm_, "[ VariableDeclaration");
       __ li(a2, 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;
       __ li(a1, Operand(Smi::FromInt(attr)));
       // Push initial value, if any.
       // Note: For variables we must not push an initial value (such as