MIPS: Move Maps' back pointers from "transitions" to "constructor" field

src/mips/macro-assembler-mips.h

Index: src/mips/macro-assembler-mips.h
diff --git a/src/mips/macro-assembler-mips.h b/src/mips/macro-assembler-mips.h
index 02845e2bbd9be0ecf82ab4265c9581aa8302a446..1bce7786c5471942cead7041476e81d0e99251e8 100644
--- a/src/mips/macro-assembler-mips.h
+++ b/src/mips/macro-assembler-mips.h
@@ -998,6 +998,11 @@ class MacroAssembler: public Assembler {
   // -------------------------------------------------------------------------
   // Support functions.
 
+  // Machine code version of Map::GetConstructor().
+  // |temp| holds |result|'s map when done, and |temp2| its instance type.
+  void GetMapConstructor(Register result, Register map, Register temp,
+                         Register temp2);
+
   // Try to get function prototype of a function and puts the value in
   // the result register. Checks that the function really is a
   // function and jumps to the miss label if the fast checks fail. The