Use entities in CommonElements interface.

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

Index: pkg/compiler/lib/src/ssa/builder_kernel.dart
diff --git a/pkg/compiler/lib/src/ssa/builder_kernel.dart b/pkg/compiler/lib/src/ssa/builder_kernel.dart
index 121be4a432d0fdc13822c73ddd1e1819835bde4e..84ae3a5f66e08605b46ffa7e2cdf411f66e99769 100644
--- a/pkg/compiler/lib/src/ssa/builder_kernel.dart
+++ b/pkg/compiler/lib/src/ssa/builder_kernel.dart
@@ -228,8 +228,8 @@ class KernelSsaBuilder extends ir.Visitor with GraphBuilder {
   HInstruction popBoolified() {
     HInstruction value = pop();
     if (typeBuilder.checkOrTrustTypes) {
-      return typeBuilder.potentiallyCheckOrTrustType(
-          value, compiler.commonElements.boolType,
+      ResolutionInterfaceType type = compiler.commonElements.boolType;
+      return typeBuilder.potentiallyCheckOrTrustType(value, type,
           kind: HTypeConversion.BOOLEAN_CONVERSION_CHECK);
     }
     HInstruction result = new HBoolify(value, commonMasks.boolType);