Reland "Add DoubleTestOp instruction"

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
diff --git a/runtime/vm/intermediate_language.cc b/runtime/vm/intermediate_language.cc
index ab7c878e846a2b9d1be3bdb19ac5608f1ed6a5f1..c3359f1f23fe46637922f5369b64a07f62f3c7f3 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -1497,6 +1497,11 @@ Definition* BinaryDoubleOpInstr::Canonicalize(FlowGraph* flow_graph) {
 }
 
 
+Definition* DoubleTestOpInstr::Canonicalize(FlowGraph* flow_graph) {
+  return HasUses() ? this : NULL;
+}
+
+
 static bool IsCommutative(Token::Kind op) {
   switch (op) {
     case Token::kMUL: