Only reference constant root list entries in the snapshot.

src/mips64/macro-assembler-mips64.cc

Index: src/mips64/macro-assembler-mips64.cc
diff --git a/src/mips64/macro-assembler-mips64.cc b/src/mips64/macro-assembler-mips64.cc
index d187fa5423702ddb8dc42648043a090d2605c48d..ef54ba5fa07d03613f80930e58b0828655aef552 100644
--- a/src/mips64/macro-assembler-mips64.cc
+++ b/src/mips64/macro-assembler-mips64.cc
@@ -89,6 +89,7 @@ void MacroAssembler::LoadRoot(Register destination,
 
 void MacroAssembler::StoreRoot(Register source,
                                Heap::RootListIndex index) {
+  DCHECK(Heap::RootCanBeWrittenAfterInitialization(index));
   sd(source, MemOperand(s6, index << kPointerSizeLog2));
 }
 
@@ -97,6 +98,7 @@ void MacroAssembler::StoreRoot(Register source,
                                Heap::RootListIndex index,
                                Condition cond,
                                Register src1, const Operand& src2) {
+  DCHECK(Heap::RootCanBeWrittenAfterInitialization(index));
   Branch(2, NegateCondition(cond), src1, src2);
   sd(source, MemOperand(s6, index << kPointerSizeLog2));
 }