Add support for compiling Dart via the FE in dart2js.

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

Index: pkg/compiler/lib/src/ssa/ssa.dart
diff --git a/pkg/compiler/lib/src/ssa/ssa.dart b/pkg/compiler/lib/src/ssa/ssa.dart
index c36361c689b41124c33e23d343f8d02358f1bfc4..5446e6ec9caeeaa1e1b4c10144cda845a5472cf4 100644
--- a/pkg/compiler/lib/src/ssa/ssa.dart
+++ b/pkg/compiler/lib/src/ssa/ssa.dart
@@ -46,7 +46,8 @@ class SsaFunctionCompiler implements FunctionCompiler {
     MemberEntity element = work.element;
     js.Expression result = generator.generateCode(work, graph, closedWorld);
     if (element is MethodElement) {
-      // TODO(sigmund): replace by kernel transformer when `useKernel` is true.
+      // TODO(sigmund): replace by kernel transformer when `useKernelInSsa` is
+      // true.
       result =
           backend.rewriteAsync(closedWorld.commonElements, element, result);
     }