fix(exception_handler): log errors via console.error

This is e.g. needed as we use this to test for errors
in our examples.

modules/angular2/src/dom/browser_adapter.dart

@@ -100,6 +100,10 @@ class BrowserDomAdapter extends GenericBrowserDomAdapter {
     setRootDomAdapter(new BrowserDomAdapter());
   }
 
+  logError(error) {
+    window.console.error(error);
+  }
+
   @override
   Map<String, String> get attrToPropMap => const <String, String>{
     'innerHtml': 'innerHtml',

modules/angular2/src/dom/browser_adapter.es6

@@ -57,6 +57,10 @@ export class BrowserDomAdapter extends GenericBrowserDomAdapter {
     setRootDomAdapter(new BrowserDomAdapter());
   }
 
+  logError(error) {
+    window.console.error(error);
+  }
+
   get attrToPropMap() {
     return _attrToPropMap;
   }

modules/angular2/src/dom/dom_adapter.js

@@ -16,6 +16,10 @@ function _abstract() {
 @ABSTRACT()
 export class DomAdapter {
 
+  logError(error) {
+    throw _abstract();
+  }
+
   /**
    * Maps attribute names to their corresponding property names for cases
    * where attribute name doesn't match property name.

modules/angular2/src/dom/html_adapter.dart

@@ -3,12 +3,17 @@ library angular2.dom.htmlAdapter;
 import 'dom_adapter.dart';
 import 'package:html/parser.dart' as parser;
 import 'package:html/dom.dart';
+import 'dart:io';
 
 class Html5LibDomAdapter implements DomAdapter {
   static void makeCurrent() {
     setRootDomAdapter(new Html5LibDomAdapter());
   }
 
+  logError(error) {
+    stderr.writeln('${error}');
+  }
+
   @override
   final attrToPropMap = const {
     'innerHtml': 'innerHtml',

modules/angular2/src/dom/parse5_adapter.cjs

@@ -28,6 +28,10 @@ export class Parse5DomAdapter extends DomAdapter {
     setRootDomAdapter(new Parse5DomAdapter());
   }
 
+  logError(error) {
+    console.error(error);
+  }
+
   get attrToPropMap() {
     return _attrToPropMap;
   }