Fix arm port of tracking field representations. Based on Rodolph Perfetta's comments

src/arm/lithium-arm.cc

Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index 16b2f095f2b62b1b3068d3e99f3333baa88afb6b..7e81ca60e8cd3d4465385d0a8cdee13da80ecce2 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -2120,9 +2120,7 @@ LInstruction* LChunkBuilder::DoStoreContextSlot(HStoreContextSlot* instr) {
 
 LInstruction* LChunkBuilder::DoLoadNamedField(HLoadNamedField* instr) {
   LOperand* obj = UseRegisterAtStart(instr->object());
-  LOperand* temp = instr->representation().IsDouble() ? TempRegister() : NULL;
-  ASSERT(temp == NULL || FLAG_track_double_fields);
-  return DefineAsRegister(new(zone()) LLoadNamedField(obj, temp));
+  return DefineAsRegister(new(zone()) LLoadNamedField(obj));
 }