Fixed a bunch of failure cases for custom elements

tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate

Index: tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate b/tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate
index 1feee18a678b0d8758e11800a10676e5ad2b1200..25a632da63d862ff321b4bd21ef0108775ad365c 100644
--- a/tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate
+++ b/tools/dom/templates/html/impl/impl_HTMLDocument.darttemplate
@@ -221,6 +221,39 @@ $if DARTIUM
     // If we're an element then everything is okay.
     return isElement ? jsClassName : null;
   }
+
+  /**
+   * Does this CustomElement class have:
+   *
+   *   - a created constructor with no arguments?
+   *   - a created constructor with a super.created() initializer?
+   *
+   * e.g.,    MyCustomClass.created() : super.created();
+   */
+  bool _hasCreatedConstructor(ClassMirror classMirror) {
+    var createdParametersValid = false;
+    var superCreatedCalled = false;
+    var className = MirrorSystem.getName(classMirror.simpleName);
+    var methodMirror = classMirror.declarations[new Symbol("$className.created")];
+    if (methodMirror != null) {
+      createdParametersValid = methodMirror.parameters.length == 0;
+
+      // Get the created constructor source and look at the initializer;
+      // Must call super.created() if not its as an error.
+      var createdSource = methodMirror.source;
+      RegExp regExp = new RegExp(r":(.*?)(;|}|\n)");
+      var match = regExp.firstMatch(createdSource);
+      superCreatedCalled = match.input.substring(match.start,match.end).contains("super.created()");
+    }
+
+    if (!superCreatedCalled) {
+      throw new DomException.jsInterop('created constructor initializer must call super.created()');
+    } else if (!createdParametersValid) {
+      throw new DomException.jsInterop('created constructor must have no parameters');
+    }
+
+    return true;
+  }
 $endif
 
   @Experimental()
@@ -281,68 +314,71 @@ $else
       throw new DomException.jsInterop("HierarchyRequestError: Only HTML elements can be customized.");
     }
 
-    // Start the hookup the JS way create an <x-foo> element that extends the
-    // <x-base> custom element. Inherit its prototype and signal what tag is
-    // inherited:
-    //
-    //     var myProto = Object.create(HTMLElement.prototype);
-    //     var myElement = document.registerElement('x-foo', {prototype: myProto});
-    var baseElement = js.context[jsClassName];
-    if (baseElement == null) {
-      // Couldn't find the HTML element so use a generic one.
-      baseElement = js.context['HTMLElement'];
-    }
-    var elemProto = js.context['Object'].callMethod("create", [baseElement['prototype']]);
-
-    // TODO(terry): Hack to stop recursion re-creating custom element when the
-    //              created() constructor of the custom element does e.g.,
-    //
-    //                  MyElement.created() : super.created() {
-    //                    this.innerHtml = "<b>I'm an x-foo-with-markup!</b>";
-    //                  }
-    //
-    //              sanitizing causes custom element to created recursively
-    //              until stack overflow.
-    //
-    //              See https://github.com/dart-lang/sdk/issues/23666
-    int creating = 0;
-    elemProto['createdCallback'] = new js.JsFunction.withThis(($this) {
-      if (_getJSClassName(reflectClass(customElementClass).superclass) != null && creating < 2) {
-        creating++;
-
-        var dartClass;
-        try {
-          dartClass = _blink.Blink_Utils.constructElement(customElementClass, $this);
-        } catch (e) {
-          dartClass = null;
-        } finally {
-          // Need to remember the Dart class that was created for this custom so
-          // return it and setup the blink_jsObject to the $this that we'll be working
-          // with as we talk to blink. 
-          $this['dart_class'] = dartClass;
-
-          creating--;
-        }
-      }
-    });
-    elemProto['attributeChangedCallback'] = new js.JsFunction.withThis(($this, attrName, oldVal, newVal) {
-      if ($this["dart_class"] != null && $this['dart_class'].attributeChanged != null) {
-        $this['dart_class'].attributeChanged(attrName, oldVal, newVal);
-      }
-    });
-    elemProto['attachedCallback'] = new js.JsFunction.withThis(($this) {
-      if ($this["dart_class"] != null && $this['dart_class'].attached != null) {
-        $this['dart_class'].attached();
+    if (_hasCreatedConstructor(classMirror)) {
+      // Start the hookup the JS way create an <x-foo> element that extends the
+      // <x-base> custom element. Inherit its prototype and signal what tag is
+      // inherited:
+      //
+      //     var myProto = Object.create(HTMLElement.prototype);
+      //     var myElement = document.registerElement('x-foo', {prototype: myProto});
+      var baseElement = js.context[jsClassName];
+      if (baseElement == null) {
+        // Couldn't find the HTML element so use a generic one.
+        baseElement = js.context['HTMLElement'];
       }
-    });
-    elemProto['detachedCallback'] = new js.JsFunction.withThis(($this) {
-      if ($this["dart_class"] != null && $this['dart_class'].detached != null) {
-        $this['dart_class'].detached();
-      }
-    });
-    // document.registerElement('x-foo', {prototype: elemProto, extends: extendsTag});
-    var jsMap = new js.JsObject.jsify({'prototype': elemProto, 'extends': extendsTag});
-    js.context['document'].callMethod('registerElement', [tag, jsMap]);
+      var elemProto = js.context['Object'].callMethod("create", [baseElement['prototype']]);
+
+      // TODO(terry): Hack to stop recursion re-creating custom element when the
+      //              created() constructor of the custom element does e.g.,
+      //
+      //                  MyElement.created() : super.created() {
+      //                    this.innerHtml = "<b>I'm an x-foo-with-markup!</b>";
+      //                  }
+      //
+      //              sanitizing causes custom element to created recursively
+      //              until stack overflow.
+      //
+      //              See https://github.com/dart-lang/sdk/issues/23666
+      int creating = 0;
+      elemProto['createdCallback'] = new js.JsFunction.withThis(($this) {
+        if (_getJSClassName(reflectClass(customElementClass).superclass) != null && creating < 2) {
+          creating++;
+
+          var dartClass;
+          try {
+            dartClass = _blink.Blink_Utils.constructElement(customElementClass, $this);
+          } catch (e) {
+            dartClass = HtmlElement.internalCreateHtmlElement();
+            throw e;
+          } finally {
+            // Need to remember the Dart class that was created for this custom so
+            // return it and setup the blink_jsObject to the $this that we'll be working
+            // with as we talk to blink. 
+            $this['dart_class'] = dartClass;
+
+            creating--;
+          }
+        }
+      });
+      elemProto['attributeChangedCallback'] = new js.JsFunction.withThis(($this, attrName, oldVal, newVal) {
+        if ($this["dart_class"] != null && $this['dart_class'].attributeChanged != null) {
+          $this['dart_class'].attributeChanged(attrName, oldVal, newVal);
+        }
+      });
+      elemProto['attachedCallback'] = new js.JsFunction.withThis(($this) {
+        if ($this["dart_class"] != null && $this['dart_class'].attached != null) {
+          $this['dart_class'].attached();
+        }
+      });
+      elemProto['detachedCallback'] = new js.JsFunction.withThis(($this) {
+        if ($this["dart_class"] != null && $this['dart_class'].detached != null) {
+          $this['dart_class'].detached();
+        }
+      });
+      // document.registerElement('x-foo', {prototype: elemProto, extends: extendsTag});
+      var jsMap = new js.JsObject.jsify({'prototype': elemProto, 'extends': extendsTag});
+      js.context['document'].callMethod('registerElement', [tag, jsMap]);
+    }
 $endif
   }