fix($compile): workaround a GC bug in Chrome < 50

In the version of V8 used in Chrome < 50, the parent of template nodes for
`transclude: "element"` directives would be improperly garbage collected
despite still having been referenced via `parentNode`.

This bug surfaced due to the introduction of lazy transclusion (652b83e),
and appears under certain circumstances when using directive start and end elements.

It should be removed some time after Chrome 50 has been released.

Fixes #14041
Closes #14286

src/ng/compile.js

@@ -2067,6 +2067,17 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
             compileNode = $compileNode[0];
             replaceWith(jqCollection, sliceArgs($template), compileNode);
 
+            // Support: Chrome < 50
+            // https://github.com/angular/angular.js/issues/14041
+
+            // In the versions of V8 prior to Chrome 50, the document fragment that is created
+            // in the `replaceWith` function is improperly garbage collected despite still
+            // being referenced by the `parentNode` property of all of the child nodes.  By adding
+            // a reference to the fragment via a different property, we can avoid that incorrect
+            // behavior.
+            // TODO: remove this line after Chrome 50 has been released
+            $template[0].$$parentNode = $template[0].parentNode;
+
             childTranscludeFn = compilationGenerator(mightHaveMultipleTransclusionError, $template, transcludeFn, terminalPriority,
                                         replaceDirective && replaceDirective.name, {
                                           // Don't pass in: