Improve handling of property loads on the proto chain.

src/mips/lithium-mips.cc

Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index 034700e58050e352fd2bbc556ffda0632f578283..6dbb6a6b563d6f0f2599aa89b36aa79a92c798fa 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -1626,10 +1626,10 @@ LInstruction* LChunkBuilder::DoCheckInstanceType(HCheckInstanceType* instr) {
 
 
 LInstruction* LChunkBuilder::DoCheckPrototypeMaps(HCheckPrototypeMaps* instr) {
-  LOperand* temp1 = TempRegister();
+  LUnallocated* temp1 = TempRegister();
   LOperand* temp2 = TempRegister();
-  LInstruction* result = new(zone()) LCheckPrototypeMaps(temp1, temp2);
-  return AssignEnvironment(result);
+  LCheckPrototypeMaps* result = new(zone()) LCheckPrototypeMaps(temp1, temp2);
+  return AssignEnvironment(Define(result, temp1));
 }