Put a snapshot of pub in the SDK.

sdk/lib/_internal/pub/test/test_pub.dart

 // Copyright (c) 2013, 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.
 
 /// Test infrastructure for testing pub. Unlike typical unit tests, most pub
 /// tests are integration tests that stage some stuff on the file system, run
 /// pub, and then validate the results. This library provides an API to build
 /// tests like that.
 library test_pub;
 
@@ skipping 371 matching lines @@
       options.environment['_PUB_TEST_TOKEN_ENDPOINT'] =
         tokenEndpoint.toString();
     }
     return options;
   });
 
   return new ScheduledProcess.start(dartBin, dartArgs, options: optionsFuture,
       description: args.isEmpty ? 'pub' : 'pub ${args.first}');
 }
 
-/// Whether pub is running from within the Dart SDK, as opposed to from the Dart
-/// source repository.
-bool get _runningFromSdk =>
-  fileExists(relativeToPub(path.join('..', '..', '..', '..', 'version')));
-
 // TODO(nweiz): use the built-in mechanism for accessing this once it exists
 // (issue 9119).
 /// The path to the `packages` directory from which pub loads its dependencies.
 String get _packageRoot {
-  if (_runningFromSdk) {
-    return path.absolute(relativeToPub(
-        path.join('..', '..', '..', '..', 'packages')));
-  } else {
-    return path.absolute(path.join(
-        path.dirname(new Options().executable), '..', '..', 'packages'));
-  }
+  return path.absolute(path.join(
+      path.dirname(new Options().executable), '..', '..', 'packages'));
 }
 
 /// Skips the current test if Git is not installed. This validates that the
 /// current test is running on a buildbot in which case we expect git to be
 /// installed. If we are not running on the buildbot, we will instead see if
 /// git is installed and skip the test if not. This way, users don't need to
 /// have git installed to run the tests locally (unless they actually care
 /// about the pub git tests).
 ///
 /// This will also increase the [Schedule] timeout to 30 seconds on Windows,
@@ skipping 208 matching lines @@
   bool matches(item, MatchState matchState) {
     if (item is! Pair) return false;
     return _firstMatcher.matches(item.first, matchState) &&
         _lastMatcher.matches(item.last, matchState);
   }
 
   Description describe(Description description) {
     description.addAll("(", ", ", ")", [_firstMatcher, _lastMatcher]);
   }
 }