Ignore redundant parallel moves when checking if a block is empty.

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 ce6092afed4789b100a15d61c894a1700ec73bdd..c9c196855c5cc66bc110e57b4ad45a0910b5be63 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -2566,6 +2566,16 @@ void ParameterInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 }
 
 
+bool ParallelMoveInstr::IsRedundant() const {
+  for (intptr_t i = 0; i < moves_.length(); i++) {
+    if (!moves_[i]->IsRedundant()) {
+      return false;
+    }
+  }
+  return true;
+}
+
+
 LocationSummary* ParallelMoveInstr::MakeLocationSummary(Isolate* isolate,
                                                         bool optimizing) const {
   return NULL;