diff --git a/dart/sync/lib/html.dart b/dart/sync/lib/html.dart
index 7e53aed0..cffda43a 100644
--- a/dart/sync/lib/html.dart
+++ b/dart/sync/lib/html.dart
@@ -89,24 +89,26 @@ class _HtmlMouse implements PageLoaderMouse {
 
   @override
   void down(int button,
-      {_ElementPageLoaderElement eventTarget, bool sync: true}) {
-    dispatchEvent('mousedown', eventTarget, button);
+      {PageLoaderElement eventTarget, bool sync: true}) {
+    dispatchEvent('mousedown', eventTarget as _ElementPageLoaderElement, button);
     loader.sync(sync);
   }
 
   @override
-  void moveTo(_ElementPageLoaderElement element, int xOffset, int yOffset,
-      {_ElementPageLoaderElement eventTarget, bool sync: true}) {
-    clientX = (element.node.getBoundingClientRect().left + xOffset).ceil();
-    clientY = (element.node.getBoundingClientRect().top + yOffset).ceil();
-    dispatchEvent('mousemove', eventTarget);
+  void moveTo(PageLoaderElement element, int xOffset, int yOffset,
+      {PageLoaderElement eventTarget, bool sync: true}) {
+    if (element is _ElementPageLoaderElement) {
+      clientX = (element.node.getBoundingClientRect().left + xOffset).ceil();
+      clientY = (element.node.getBoundingClientRect().top + yOffset).ceil();
+    }
+    dispatchEvent('mousemove', eventTarget as _ElementPageLoaderElement);
     loader.sync(sync);
   }
 
   @override
   void up(int button,
-      {_ElementPageLoaderElement eventTarget, bool sync: true}) {
-    dispatchEvent('mouseup', eventTarget);
+      {PageLoaderElement eventTarget, bool sync: true}) {
+    dispatchEvent('mouseup', eventTarget as _ElementPageLoaderElement);
     loader.sync(sync);
   }
 
@@ -220,11 +222,11 @@ class _ElementPageLoaderElement extends HtmlPageLoaderElement {
   final PageLoaderAttributes style;
 
   _ElementPageLoaderElement(Element _node, HtmlPageLoader loader)
-      : super._(loader),
-        this.node = _node,
+      : this.node = _node,
         this.attributes = new _ElementAttributes(_node),
         this.computedStyle = new _ElementComputedStyle(_node),
-        this.style = new _ElementStyle(_node);
+        this.style = new _ElementStyle(_node),
+        super._(loader);
 
   @override
   PageLoaderElement get shadowRoot {
@@ -268,7 +270,7 @@ class _ElementPageLoaderElement extends HtmlPageLoaderElement {
     _fireKeyPressEvents(node, keys);
     if (node is InputElement || node is TextAreaElement) {
       // suppress warning by hiding field
-      var node = this.node;
+      dynamic node = this.node;
       var value = node.value + keys;
       node.value = '';
       node.dispatchEvent(new TextEvent('textInput', data: value));
@@ -280,7 +282,7 @@ class _ElementPageLoaderElement extends HtmlPageLoaderElement {
   @override
   void clear({bool sync: true}) {
     if (node is InputElement || node is TextAreaElement) {
-      var node = this.node;
+      dynamic node = this.node;
       node.value = '';
       node.dispatchEvent(new TextEvent('textInput', data: ''));
     } else {
diff --git a/dart/sync/lib/src/annotations.dart b/dart/sync/lib/src/annotations.dart
index 6532c4ee..546b6a72 100644
--- a/dart/sync/lib/src/annotations.dart
+++ b/dart/sync/lib/src/annotations.dart
@@ -108,7 +108,7 @@ class InShadowDom implements Finder {
     }
     candidates = candidates.map((candidate) => candidate.shadowRoot);
     if (find != null) {
-      var newCandidates = new Set();
+      var newCandidates = new Set<PageLoaderElement>();
       for (var candidate in candidates) {
         newCandidates.addAll(find.findElements(candidate));
       }
@@ -336,7 +336,7 @@ class Chain implements Finder {
           newElements.addAll(annotation.findElements(element));
         }
       }
-      elements = newElements;
+      elements = newElements.toList();
     }
 
     return new UnmodifiableListView<PageLoaderElement>(elements);
diff --git a/dart/sync/lib/webdriver.dart b/dart/sync/lib/webdriver.dart
index 704665ff..350c04cb 100644
--- a/dart/sync/lib/webdriver.dart
+++ b/dart/sync/lib/webdriver.dart
@@ -31,8 +31,8 @@ class WebDriverPageLoader extends BasePageLoader {
   final _WebDriverMouse mouse;
 
   WebDriverPageLoader(wd.SearchContext globalContext, {useShadowDom: true})
-      : super(clock: const _IOClock(), useShadowDom: useShadowDom),
-        this.mouse = new _WebDriverMouse(globalContext.driver) {
+      : this.mouse = new _WebDriverMouse(globalContext.driver),
+        super(clock: const _IOClock(), useShadowDom: useShadowDom) {
     this._globalContext = new WebDriverPageLoaderElement(globalContext, this);
   }
 
@@ -59,32 +59,35 @@ class _WebDriverMouse implements PageLoaderMouse {
 
   @override
   void down(int button,
-      {_WebElementPageLoaderElement eventTarget, bool sync: true}) {
+      {PageLoaderElement eventTarget, bool sync: true}) {
     if (eventTarget == null) {
       driver.mouse.down(button);
     } else {
-      _fireEvent(eventTarget, 'mousedown', button);
+      _fireEvent(
+        eventTarget as _WebElementPageLoaderElement, 'mousedown', button);
     }
   }
 
   @override
-  void moveTo(_WebElementPageLoaderElement element, int xOffset, int yOffset,
-      {_WebElementPageLoaderElement eventTarget, bool sync: true}) {
+  void moveTo(PageLoaderElement element, int xOffset, int yOffset,
+      {PageLoaderElement eventTarget, bool sync: true}) {
     if (eventTarget != null) {
       throw new ArgumentError(
           'eventTarget not supported on WebDriverPageLoader.mouse.moveTo');
     }
     driver.mouse
-        .moveTo(element: element.context, xOffset: xOffset, yOffset: yOffset);
+        .moveTo(element: (element as _WebElementPageLoaderElement).context,
+                xOffset: xOffset, yOffset: yOffset);
   }
 
   @override
   void up(int button,
-      {_WebElementPageLoaderElement eventTarget, bool sync: true}) {
+      {PageLoaderElement eventTarget, bool sync: true}) {
     if (eventTarget == null) {
       driver.mouse.up(button);
     } else {
-      _fireEvent(eventTarget, 'mouseup', button);
+      _fireEvent(
+        eventTarget as _WebElementPageLoaderElement, 'mouseup', button);
     }
   }
 
@@ -153,11 +156,11 @@ class _WebElementPageLoaderElement extends WebDriverPageLoaderElement {
 
   _WebElementPageLoaderElement(
       wd.WebElement _context, WebDriverPageLoader loader)
-      : super._(loader),
-        this.context = _context,
+      : this.context = _context,
         this.attributes = new _ElementAttributes(_context),
         this.computedStyle = new _ElementComputedStyle(_context),
-        this.style = new _ElementStyle(_context);
+        this.style = new _ElementStyle(_context),
+        super._(loader);
 
   @override
   WebDriverPageLoaderElement get shadowRoot {
@@ -257,7 +260,7 @@ class _ShadowRootPageLoaderElement extends WebDriverPageLoaderElement {
   bool get displayed => context.displayed;
 
   @override
-  List<PageLoaderElement> getElementsByCss(String selector) =>
+  List<WebDriverPageLoaderElement> getElementsByCss(String selector) =>
       _fromContextList(_execute('.querySelectorAll("$selector")'));
 
   dynamic _execute(String script) {