Remove now unused --unparse-validation flag.

lib/compiler/implementation/apiimpl.dart

Index: lib/compiler/implementation/apiimpl.dart
diff --git a/lib/compiler/implementation/apiimpl.dart b/lib/compiler/implementation/apiimpl.dart
index f41bbe541524b3a1b3210c1eb470ffeecf2d78a7..b162a506875d69d023936f8bc2b786a8e9507163 100644
--- a/lib/compiler/implementation/apiimpl.dart
+++ b/lib/compiler/implementation/apiimpl.dart
@@ -29,8 +29,7 @@ class Compiler extends leg.Compiler {
           tracer: new ssa.HTracer(),
           enableTypeAssertions: options.indexOf('--enable-checked-mode') != -1,
           enableUserAssertions: options.indexOf('--enable-checked-mode') != -1,
-          emitJavascript: options.indexOf('--output-type=dart') == -1,
-          validateUnparse: options.indexOf('--unparse-validation') !== -1);
+          emitJavascript: options.indexOf('--output-type=dart') == -1);
 
   elements.LibraryElement scanBuiltinLibrary(String path) {
     Uri uri = libraryRoot.resolve(DART2JS_LIBRARY_MAP[path].libraryPath);