do not suggest elements from internal sdk libs

pkg/analysis_server/test/mock_sdk.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library testing.mock_sdk;
 
 import 'package:analyzer/file_system/file_system.dart' as resource;
 import 'package:analyzer/file_system/memory_file_system.dart' as resource;
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 class MockSdk implements DartSdk {
   static const _MockSdkLibrary LIB_CORE = const _MockSdkLibrary('dart:core',
       '/lib/core/core.dart', '''
 library dart.core;
 
 import 'dart:async';
+import 'dart:_internal';
 
 class Object {
   bool operator ==(other) => identical(this, other);
   String toString() => 'a string';
   int get hashCode => 0;
 }
 
 class Function {}
 class StackTrace {}
 class Symbol {}
@@ skipping 108 matching lines @@
 
   static const _MockSdkLibrary LIB_MATH = const _MockSdkLibrary('dart:math',
       '/lib/math/math.dart', '''
 library dart.math;
 const double E = 2.718281828459045;
 const double PI = 3.1415926535897932;
 const double LN10 =  2.302585092994046;
 num min(num a, num b) => 0;
 num max(num a, num b) => 0;
 external double cos(num x);
+external num pow(num x, num exponent);
 external double sin(num x);
 external double sqrt(num x);
 class Random {
   bool nextBool() => true;
   double nextDouble() => 2.0;
   int nextInt() => 1;
 }
 ''');
 
   static const _MockSdkLibrary LIB_HTML = const _MockSdkLibrary('dart:html',
       '/lib/html/dartium/html_dartium.dart', '''
 library dart.html;
 class HtmlElement {}
 ''');
 
+  static const _MockSdkLibrary LIB_INTERNAL = const _MockSdkLibrary(
+      'dart:_internal', '/lib/internal/internal.dart', '''
+library dart._internal;
+external void printToConsole(String line);
+''');
+
   static const List<SdkLibrary> LIBRARIES = const [
     LIB_CORE,
     LIB_ASYNC,
     LIB_COLLECTION,
     LIB_CONVERT,
     LIB_MATH,
     LIB_HTML,
+    LIB_INTERNAL,
   ];
 
   final resource.MemoryResourceProvider provider =
       new resource.MemoryResourceProvider();
 
   /**
    * The [AnalysisContext] which is used for all of the sources.
    */
   InternalAnalysisContext _analysisContext;
 
@@ skipping 78 matching lines @@
   }
 
   @override
   Source mapDartUri(String dartUri) {
     const Map<String, String> uriToPath = const {
       "dart:core": "/lib/core/core.dart",
       "dart:html": "/lib/html/dartium/html_dartium.dart",
       "dart:async": "/lib/async/async.dart",
       "dart:collection": "/lib/collection/collection.dart",
       "dart:convert": "/lib/convert/convert.dart",
-      "dart:math": "/lib/math/math.dart"
+      "dart:math": "/lib/math/math.dart",
+      "dart:_internal": "/lib/internal/internal.dart",
     };
 
     String path = uriToPath[dartUri];
     if (path != null) {
       resource.File file = provider.getResource(path);
       Uri uri = new Uri(scheme: 'dart', path: dartUri.substring(5));
       return file.createSource(uri);
     }
 
     // If we reach here then we tried to use a dartUri that's not in the
@@ skipping 15 matching lines @@
   @override
   bool get isDart2JsLibrary => throw unimplemented;
 
   @override
   bool get isDocumented => throw unimplemented;
 
   @override
   bool get isImplementation => throw unimplemented;
 
   @override
-  bool get isInternal => throw unimplemented;
+  bool get isInternal => shortName.startsWith('dart:_');
 
   @override
   bool get isShared => throw unimplemented;
 
   @override
   bool get isVmLibrary => throw unimplemented;
 
   UnimplementedError get unimplemented => new UnimplementedError();
 }