dart2js: Insert HTypeKnown refinement nodes on dominated edges of HPhi nodes.

pkg/compiler/lib/src/ssa/types_propagation.dart

Index: pkg/compiler/lib/src/ssa/types_propagation.dart
diff --git a/pkg/compiler/lib/src/ssa/types_propagation.dart b/pkg/compiler/lib/src/ssa/types_propagation.dart
index 49aa6f99cf3d19f255376d32cdcc2a7465b6ea71..1ce075a5df9a8c08b201a149f0582e31e5f1e979 100644
--- a/pkg/compiler/lib/src/ssa/types_propagation.dart
+++ b/pkg/compiler/lib/src/ssa/types_propagation.dart
@@ -397,7 +397,9 @@ class SsaTypePropagator extends HBaseVisitor implements OptimizationPhase {
           addDependentInstructionsToWorkList(next);
         }
       } else {
-        bool hasCandidates() => receiver.dominatedUsers(instruction).length > 1;
+        bool hasCandidates() => DominatedUses
+            .of(receiver, instruction, excludeDominator: true)
+            .isNotEmpty;
 
         if ((receiver.usedBy.length <= _MAX_QUICK_USERS)
             ? (hasCandidates() && computeNewType() != receiverType)