Remove the compiled_transitions flag and cleanup the unused code.

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 6f45b81082a93fe5eda2d44901872425a49f215c..7f0ed3dbaeaafe00f3924c307a96a6e431d4d7d9 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -4288,7 +4288,7 @@ void LCodeGen::DoTransitionElementsKind(LTransitionElementsKind* instr) {
     ASSERT_NE(instr->temp(), NULL);
     __ RecordWriteField(object_reg, HeapObject::kMapOffset, new_map_reg,
                         ToRegister(instr->temp()), kDontSaveFPRegs);
-  } else if (FLAG_compiled_transitions) {
+  } else {
     PushSafepointRegistersScope scope(this);
     if (!object_reg.is(rax)) {
       __ movq(rax, object_reg);
@@ -4298,28 +4298,6 @@ void LCodeGen::DoTransitionElementsKind(LTransitionElementsKind* instr) {
     __ CallStub(&stub);
     RecordSafepointWithRegisters(
         instr->pointer_map(), 0, Safepoint::kNoLazyDeopt);
-  } else if (IsFastSmiElementsKind(from_kind) &&
-            IsFastDoubleElementsKind(to_kind)) {
-    Register fixed_object_reg = ToRegister(instr->temp());
-    ASSERT(fixed_object_reg.is(rdx));
-    Register new_map_reg = ToRegister(instr->new_map_temp());
-    ASSERT(new_map_reg.is(rbx));
-    __ movq(new_map_reg, to_map, RelocInfo::EMBEDDED_OBJECT);
-    __ movq(fixed_object_reg, object_reg);
-    CallCode(isolate()->builtins()->TransitionElementsSmiToDouble(),
-             RelocInfo::CODE_TARGET, instr);
-  } else if (IsFastDoubleElementsKind(from_kind) &&
-             IsFastObjectElementsKind(to_kind)) {
-    Register fixed_object_reg = ToRegister(instr->temp());
-    ASSERT(fixed_object_reg.is(rdx));
-    Register new_map_reg = ToRegister(instr->new_map_temp());
-    ASSERT(new_map_reg.is(rbx));
-    __ movq(new_map_reg, to_map, RelocInfo::EMBEDDED_OBJECT);
-    __ movq(fixed_object_reg, object_reg);
-    CallCode(isolate()->builtins()->TransitionElementsDoubleToObject(),
-             RelocInfo::CODE_TARGET, instr);
-  } else {
-    UNREACHABLE();
   }
   __ bind(&not_applicable);
 }