feat(ChangeDetector): Add support for short-circuiting

modules_dart/transform/lib/src/transform/template_compiler/change_detector_codegen.dart

@@ -14,6 +14,7 @@ import 'package:angular2/src/core/change_detection/binding_record.dart';
 import 'package:angular2/src/core/change_detection/codegen_facade.dart'
     show codify;
 import 'package:angular2/src/core/facade/exceptions.dart' show BaseException;
+import 'package:angular2/src/core/facade/collection.dart' show ListWrapper;
 
 /// Responsible for generating change detector classes for Angular 2.
 ///
@@ -90,6 +91,7 @@ class _CodegenState {
   final CodegenNameUtil _names;
   final ChangeDetectorGenConfig _genConfig;
   final List<BindingTarget> _propertyBindingTargets;
+  final List<int> _endOfBlockIdxs = [];
 
   String get _changeDetectionStrategyAsCode => _changeDetectionStrategy == null
       ? 'null'
@@ -156,7 +158,7 @@ class _CodegenState {
           var $_IS_CHANGED_LOCAL = false;
           var $_CHANGES_LOCAL = null;
 
-          ${_records.map(_genRecord).join('')}
+          ${_genAllRecords()}
         }
 
         ${_maybeGenHandleEventInternal()}
@@ -186,6 +188,15 @@ class _CodegenState {
     ''');
   }
 
+  String _genAllRecords() {
+    _endOfBlockIdxs.clear();
+    List<String> res = [];
+    for (int i = 0; i < _records.length; i++) {
+      res.add(_genRecord(_records[i], i));
+    }
+    return res.join('');
+  }
+
   String _genPropertyBindingTargets() {
     var targets = _logic.genPropertyBindingTargets(
         _propertyBindingTargets, this._genConfig.genDebugInfo);
@@ -215,10 +226,29 @@ class _CodegenState {
   }
 
   String _genEventBinding(EventBinding eb) {
-    var recs = eb.records.map((r) => _genEventBindingEval(eb, r)).join("\n");
+    List<String> codes = [];
+    _endOfBlockIdxs.clear();
+
+    ListWrapper.forEachWithIndex(eb.records, (r, i) {
+      var code;
+      var r = eb.records[i];
+
+      if (r.isConditionalSkipRecord()) {
+        code = _genConditionalSkip(r, _names.getEventLocalName(eb, i));
+      } else if (r.isUnconditionalSkipRecord()) {
+        code = _genUnconditionalSkip(r);
+      } else {
+        code = _genEventBindingEval(eb, r);
+      }
+
+      code += this._genEndOfSkipBlock(i);
+
+      codes.add(code);
+    });
+
     return '''
     if (eventName == "${eb.eventName}" && elIndex == ${eb.elIndex}) {
-    ${recs}
+    ${codes.join("\n")}
     }''';
   }
 
@@ -315,20 +345,53 @@ class _CodegenState {
     return 'var ${declareNames.join(', ')};';
   }
 
-  String _genRecord(ProtoRecord r) {
-    var rec = null;
+  String _genRecord(ProtoRecord r, int index) {
+    var code = null;
     if (r.isLifeCycleRecord()) {
-      rec = _genDirectiveLifecycle(r);
+      code = _genDirectiveLifecycle(r);
     } else if (r.isPipeRecord()) {
-      rec = _genPipeCheck(r);
+      code = _genPipeCheck(r);
+    } else if (r.isConditionalSkipRecord()) {
+      code = _genConditionalSkip(r, _names.getLocalName(r.contextIndex));
+    } else if (r.isUnconditionalSkipRecord()) {
+      code = _genUnconditionalSkip(r);
     } else {
-      rec = _genReferenceCheck(r);
+      code = _genReferenceCheck(r);
     }
-    return '''
+
+    code = '''
       ${this._maybeFirstInBinding(r)}
-      ${rec}
+      ${code}
       ${this._maybeGenLastInDirective(r)}
+      ${this._genEndOfSkipBlock(index)}
     ''';
+
+    return code;
+  }
+
+  String _genConditionalSkip(ProtoRecord r, String condition) {
+    var maybeNegate = r.mode == RecordType.SkipRecordsIf ? '!' : '';
+    _endOfBlockIdxs.add(r.fixedArgs[0] - 1);
+
+    return 'if ($maybeNegate$condition) {';
+  }
+
+  String _genUnconditionalSkip(ProtoRecord r) {
+    _endOfBlockIdxs.removeLast();
+    _endOfBlockIdxs.add(r.fixedArgs[0] - 1);
+    return '} else {';
+  }
+
+  String _genEndOfSkipBlock(int protoIndex) {
+    if (!ListWrapper.isEmpty(this._endOfBlockIdxs)) {
+      var endOfBlock = ListWrapper.last(this._endOfBlockIdxs);
+      if (protoIndex == endOfBlock) {
+        this._endOfBlockIdxs.removeLast();
+        return '}';
+      }
+    }
+
+    return '';
   }
 
   String _genDirectiveLifecycle(ProtoRecord r) {