Add FunctionEntity.asyncMarker and refactor SourceInformationStrategy to avoid ResolvedAst

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

Index: pkg/compiler/lib/src/ssa/builder.dart
diff --git a/pkg/compiler/lib/src/ssa/builder.dart b/pkg/compiler/lib/src/ssa/builder.dart
index 1b3c4c6d89eca097f3c2b1e5a27380f030c4e2b3..4a8d1a93ebec29693a6109c6b5e4e8384782803b 100644
--- a/pkg/compiler/lib/src/ssa/builder.dart
+++ b/pkg/compiler/lib/src/ssa/builder.dart
@@ -271,7 +271,7 @@ class SsaBuilder extends ast.Visitor
     graph.element = target;
     sourceElementStack.add(target);
     sourceInformationBuilder =
-        sourceInformationFactory.createBuilderForContext(resolvedAst);
+        sourceInformationFactory.createBuilderForContext(target);
     graph.sourceInformation =
         sourceInformationBuilder.buildVariableDeclaration();
     localsHandler = new LocalsHandler(
@@ -665,8 +665,7 @@ class SsaBuilder extends ast.Visitor
       // The [sourceElementStack] contains declaration elements.
       SourceInformationBuilder oldSourceInformationBuilder =
           sourceInformationBuilder;
-      sourceInformationBuilder =
-          sourceInformationBuilder.forContext(resolvedAst);
+      sourceInformationBuilder = sourceInformationBuilder.forContext(element);
       sourceElementStack.add(element.declaration);
       var result = f();
       sourceInformationBuilder = oldSourceInformationBuilder;