Cache some global constants in Thread, to allow access via THR register.

runtime/vm/assembler_ia32.cc

Index: runtime/vm/assembler_ia32.cc
diff --git a/runtime/vm/assembler_ia32.cc b/runtime/vm/assembler_ia32.cc
index 249fba089e486e0fd03a0974c1726f857a3922f1..13dfb9b590437967eb8f1632491386012468c23d 100644
--- a/runtime/vm/assembler_ia32.cc
+++ b/runtime/vm/assembler_ia32.cc
@@ -2157,6 +2157,16 @@ void Assembler::LoadIsolate(Register dst) {
 }
 
 
+void Assembler::LoadBoolTrue(Register dst) {
+  movl(dst, Address(THR, Thread::bool_true_offset()));
+}
+
+
+void Assembler::LoadBoolFalse(Register dst) {
+  movl(dst, Address(THR, Thread::bool_false_offset()));
+}
+
+
 void Assembler::LoadObject(Register dst, const Object& object) {
   if (object.IsSmi() || object.InVMHeap()) {
     movl(dst, Immediate(reinterpret_cast<int32_t>(object.raw())));