Lesser direct Compiler use in SSA

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 e3b2a02cf800623c3f3303474362925d8b3ab203..e0cafecaf3acd2b6ce67cf877f347fae961868d0 100644
--- a/pkg/compiler/lib/src/ssa/builder_kernel.dart
+++ b/pkg/compiler/lib/src/ssa/builder_kernel.dart
@@ -115,6 +115,8 @@ class KernelSsaBuilder extends ir.Visitor with GraphBuilder {
 
   HInstruction rethrowableException;
 
+  final Compiler compiler;
+
   @override
   JavaScriptBackend get backend => compiler.backend;
 
@@ -136,12 +138,11 @@ class KernelSsaBuilder extends ir.Visitor with GraphBuilder {
   KernelSsaBuilder(
       this.targetElement,
       this.resolvedAst,
-      Compiler compiler,
+      this.compiler,
       this.closedWorld,
       this.registry,
       SourceInformationStrategy sourceInformationFactory,
       Kernel kernel) {
-    this.compiler = compiler;
     this.loopHandler = new KernelLoopHandler(this);
     typeBuilder = new TypeBuilder(this);
     graph.element = targetElement;