fix(test_lib): run unit tests in default Documnent

Closes angular#3501
Fixes angular#3475

Author: marclaval

modules/angular2/src/test_lib/test_component_builder.ts

@@ -138,6 +138,10 @@ export class TestComponentBuilder {
     var doc = this._injector.get(DOCUMENT_TOKEN);
 
     // TODO(juliemr): can/should this be optional?
+    var oldRoots = DOM.querySelectorAll(doc, '[id^=root]');
+    for (var i = 0; i < oldRoots.length; i++) {
+      DOM.remove(oldRoots[i]);
+    }
     DOM.appendChild(doc.body, rootEl);
 
 

modules/angular2/src/test_lib/test_injector.ts

@@ -93,7 +93,7 @@ function _getAppBindings() {
 
   // The document is only available in browser environment
   try {
-    appDoc = DOM.createHtmlDocument();
+    appDoc = DOM.defaultDoc();
   } catch (e) {
     appDoc = null;
   }

modules/angular2/test/forms/integration_spec.ts

@@ -736,11 +736,6 @@ export function main() {
                   rootTC.componentInstance.form = form;
                   rootTC.detectChanges();
 
-                  // In IE, the element needs to be appended to the real DOM,
-                  // otherwise setting .selectionStart fails with "unspecified error"
-                  var isIE = DOM.getUserAgent().indexOf("Trident") > -1;
-                  if (isIE) DOM.appendChild(DOM.defaultDoc().body, rootTC.nativeElement);
-
                   var input = rootTC.query(By.css("input")).nativeElement;
                   input.value = "aa";
                   input.selectionStart = 1;
@@ -751,7 +746,6 @@ export function main() {
 
                   // selection start has not changed because we did not reset the value
                   expect(input.selectionStart).toEqual(1);
-                  if (isIE) DOM.removeChild(DOM.defaultDoc().body, rootTC.nativeElement);
                 })));
     });
   });