fix(dart/transform): Gracefully handle log calls before init

- Lazily create and use a logger that prints instead of `throw`ing.
- Use this logger in unit tests.

modules/angular2/src/transform/common/logging.dart

@@ -18,7 +18,37 @@ void setLogger(BuildLogger logger) {
 /// The logger the transformer should use for messaging.
 BuildLogger get logger {
   if (_logger == null) {
-    throw new StateError('Logger never initialized.');
+    _logger = new PrintLogger();
   }
   return _logger;
 }
+
+class PrintLogger implements BuildLogger {
+  void _printWithPrefix(prefix, msg) => print('$prefix: $msg');
+  void info(msg, {AssetId asset, SourceSpan span}) =>
+      _printWithPrefix('INFO', msg);
+  void fine(msg, {AssetId asset, SourceSpan span}) =>
+      _printWithPrefix('FINE', msg);
+  void warning(msg, {AssetId asset, SourceSpan span}) =>
+      _printWithPrefix('WARN', msg);
+  void error(msg, {AssetId asset, SourceSpan span}) {
+    throw new PrintLoggerError(msg, asset, span);
+  }
+  Future writeOutput() => null;
+  Future addLogFilesFromAsset(AssetId id, [int nextNumber = 1]) => null;
+}
+
+class PrintLoggerError extends Error {
+  final String message;
+  final AssetId asset;
+  final SourceSpan span;
+
+  PrintLoggerError(message, asset, span);
+
+  @override
+  String toString() {
+    return 'Message: ${Error.safeToString(message)}, '
+        'Asset: ${Error.safeToString(asset)}, '
+        'Span: ${Error.safeToString(span)}.';
+  }
+}

modules/angular2/test/transform/common/logger.dart

@@ -1,23 +0,0 @@
-library angular2.test.transform.common.logger;
-
-import 'package:code_transformers/messages/build_logger.dart';
-
-class NullLogger implements BuildLogger {
-  const NullLogger();
-  void info(String message, {AssetId asset, SourceSpan span}) {}
-  void fine(String message, {AssetId asset, SourceSpan span}) {}
-  void warning(String message, {AssetId asset, SourceSpan span}) {}
-  void error(String message, {AssetId asset, SourceSpan span}) {
-    throw new NullLoggerError(message, asset, span);
-  }
-  Future writeOutput() => null;
-  Future addLogFilesFromAsset(AssetId id, [int nextNumber = 1]) => null;
-}
-
-class NullLoggerError extends Error {
-  final String message;
-  final AssetId asset;
-  final SourceSpan span;
-
-  NullLoggerError(message, asset, span);
-}

modules/angular2/test/transform/directive_linker/all_tests.dart

@@ -10,14 +10,12 @@ import 'package:path/path.dart' as path;
 import 'package:guinness/guinness.dart';
 import 'package:unittest/vm_config.dart';
 
-import '../common/logger.dart';
 import '../common/read_file.dart';
 
 var formatter = new DartFormatter();
 
 void allTests() {
   var reader = new TestAssetReader();
-  setLogger(new NullLogger());
 
   it('should ensure that dependencies are property chained.', () async {
     for (var inputPath in [

modules/angular2/test/transform/template_compiler/all_tests.dart

@@ -9,7 +9,6 @@ import 'package:angular2/src/transform/template_compiler/generator.dart';
 import 'package:dart_style/dart_style.dart';
 import 'package:guinness/guinness.dart';
 
-import '../common/logger.dart';
 import '../common/read_file.dart';
 
 var formatter = new DartFormatter();
@@ -17,7 +16,6 @@ var formatter = new DartFormatter();
 void allTests() {
   Html5LibDomAdapter.makeCurrent();
   AssetReader reader = new TestAssetReader();
-  setLogger(new NullLogger());
 
   it('should parse simple expressions in inline templates.', () async {
     var inputPath =