Manually check if a constructor has no body in the backend: either ends with ';', or has not statem…

lib/compiler/implementation/ssa/builder.dart

Index: lib/compiler/implementation/ssa/builder.dart
===================================================================
--- lib/compiler/implementation/ssa/builder.dart	(revision 7445)
+++ lib/compiler/implementation/ssa/builder.dart	(working copy)
@@ -817,7 +817,12 @@
     assert(constructor.kind === ElementKind.GENERATIVE_CONSTRUCTOR);
     if (constructor is SynthesizedConstructorElement) return null;
     FunctionExpression node = constructor.parseNode(compiler);
-    if (!node.hasBody()) return null;
+    // If we know the body doesn't have any code, we don't generate
+    // it.
+    if (node.body.asBlock() !== null) {
+      NodeList statements = node.body.asBlock().statements;
+      if (statements.isEmpty()) return null;
+    }
     ClassElement classElement = constructor.enclosingElement;
     ConstructorBodyElement bodyElement;
     for (Link<Element> backendMembers = classElement.backendMembers;