MIPS: Reland and fix "Fix LoadFieldByIndex to take mutable heap-numbers into account."

src/mips/lithium-codegen-mips.h

Index: src/mips/lithium-codegen-mips.h
diff --git a/src/mips/lithium-codegen-mips.h b/src/mips/lithium-codegen-mips.h
index 63f0661ae53e6c0a31070496c57b3cf1e7c70125..691559a11a5bba82a184b108e9135152bd38f401 100644
--- a/src/mips/lithium-codegen-mips.h
+++ b/src/mips/lithium-codegen-mips.h
@@ -140,6 +140,10 @@ class LCodeGen: public LCodeGenBase {
                                        Label* map_check);
 
   void DoDeferredInstanceMigration(LCheckMaps* instr, Register object);
+  void DoDeferredLoadMutableDouble(LLoadFieldByIndex* instr,
+                                   Register result,
+                                   Register object,
+                                   Register index);
 
   // Parallel move support.
   void DoParallelMove(LParallelMove* move);