fix(transformer): Loggers now are per zone and each transform runs in its own zone

modules/angular2/src/transform/reflection_remover/rewriter.dart

@@ -45,8 +45,7 @@ class Rewriter {
 ///
 /// This breaks our dependency on dart:mirrors, which enables smaller code
 /// size and better performance.
-class _RewriterVisitor extends Object
-    with RecursiveAstVisitor<Object> {
+class _RewriterVisitor extends Object with RecursiveAstVisitor<Object> {
   final Rewriter _rewriter;
   final buf = new StringBuffer();
   final reflectionCapabilityAssignments = [];

modules/angular2/src/transform/reflection_remover/transformer.dart

@@ -30,9 +30,7 @@ class ReflectionRemover extends Transformer {
 
   @override
   Future apply(Transform transform) async {
-    log.init(transform);
-
-    try {
+    await log.initZoned(transform, () async {
       var newEntryPoints = options.entryPoints.map((entryPoint) {
         return new AssetId(transform.primaryInput.id.package, entryPoint)
             .changeExtension(DEPS_EXTENSION);
@@ -54,10 +52,6 @@ class ReflectionRemover extends Transformer {
           mirrorMode: mirrorMode, writeStaticInit: writeStaticInit);
       transform.addOutput(
           new Asset.fromString(transform.primaryInput.id, transformedCode));
-    } catch (ex, stackTrace) {
-      log.logger.error('Removing reflection failed.\n'
-          'Exception: $ex\n'
-          'Stack Trace: $stackTrace');
-    }
+    }, errorMessage: 'Removing reflection failed.');
   }
 }