Disable tracking of double fields during snapshot creation.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 131cbb8f5086b5fad31e282bc4bbfea6ceb737d4..5d1ad6a3cbd0cf0ab90c26b833e5780422e13b33 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -2815,8 +2815,7 @@ void LCodeGen::DoLoadNamedField(LLoadNamedField* instr) {
   }
 
   Register object = ToRegister(instr->object());
-  if (FLAG_track_double_fields &&
-      instr->hydrogen()->representation().IsDouble()) {
+  if (instr->hydrogen()->representation().IsDouble()) {
     XMMRegister result = ToDoubleRegister(instr->result());
     __ movsd(result, FieldOperand(object, offset));
     return;
@@ -3967,7 +3966,7 @@ void LCodeGen::DoStoreNamedField(LStoreNamedField* instr) {
         DeoptimizeIf(cc, instr->environment());
       }
     }
-  } else if (FLAG_track_double_fields && representation.IsDouble()) {
+  } else if (representation.IsDouble()) {
     ASSERT(transition.is_null());
     ASSERT(access.IsInobject());
     ASSERT(!hinstr->NeedsWriteBarrier());