Handle deferred access as pre-step in SemanticSendVisitor.

pkg/compiler/lib/src/resolution/resolution_result.dart

Index: pkg/compiler/lib/src/resolution/resolution_result.dart
diff --git a/pkg/compiler/lib/src/resolution/resolution_result.dart b/pkg/compiler/lib/src/resolution/resolution_result.dart
index ba2b74cdd58c5eb91f5034e791bcf2787ef7e485..4b12234016736a1f1fc0305a374c59ecd87b3fa4 100644
--- a/pkg/compiler/lib/src/resolution/resolution_result.dart
+++ b/pkg/compiler/lib/src/resolution/resolution_result.dart
@@ -10,6 +10,7 @@ enum ResultKind {
   TYPE,
   ASSERT,
   CONSTANT,
+  PREFIX,
 }
 
 /// The result of resolving a node.
@@ -30,13 +31,32 @@ abstract class ResolutionResult {
   bool get isConstant => false;
 }
 
+/// The prefix of top level or member access, like `prefix.member`,
+/// `prefix.Class.member` or `Class.member`.
+class PrefixResult extends ResolutionResult {
+  final PrefixElement prefix;
+  final ClassElement cls;
+
+  PrefixResult(this.prefix, this.cls);
+
+  Element get element => cls != null ? cls : prefix;
+
+  bool get isDeferred => prefix != null && prefix.isDeferred;
+
+  ResultKind get kind => ResultKind.PREFIX;
+
+  String toString() => 'PrefixResult($prefix,$cls)';
+}
+
 /// The result for the resolution of a node that points to an [Element].
 class ElementResult extends ResolutionResult {
   final Element element;
 
   ResultKind get kind => ResultKind.ELEMENT;
 
-  ElementResult(this.element);
+  ElementResult(this.element) {
+    assert(element != null);
+  }
 
   String toString() => 'ElementResult($element)';
 }