Fix the content_browsertests everywhere maybe.

content/browser/web_contents/web_contents_view_aura.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/web_contents/web_contents_view_aura.h"
 
 #include "base/auto_reset.h"
 #include "base/utf_string_conversions.h"
 #include "content/browser/renderer_host/dip_util.h"
 #include "content/browser/renderer_host/overscroll_controller.h"
@@ skipping 723 matching lines @@
     const gfx::Size& initial_size, gfx::NativeView context) {
   // NOTE: we ignore |initial_size| since in some cases it's wrong (such as
   // if the bookmark bar is not shown and you create a new tab). The right
   // value is set shortly after this, so its safe to ignore.
 
   window_.reset(new aura::Window(this));
   window_->set_owned_by_parent(false);
   window_->SetType(aura::client::WINDOW_TYPE_CONTROL);
   window_->SetTransparent(false);
   window_->Init(ui::LAYER_NOT_DRAWN);
-  // TODO(mukai, erg): Should use a non-NULL value later when the DCHECK is
-  // turned on in SetDefaultParentByRootWindow().
-  aura::RootWindow* target_root = context ? context->GetRootWindow() : NULL;
-  window_->SetDefaultParentByRootWindow(target_root, gfx::Rect());
+  if (context) {
+    // There are places where there is no context currently because object
+    // hierarchies are built before they're attached to a Widget. (See
+    // views::WebView as an example; GetWidget() returns NULL at the point
+    // where we are created.)
+    //
+    // It should be OK to not set a default parent since such users will
+    // explicitly add this WebContentsViewAura to their tree after they create
+    // us.
+    window_->SetDefaultParentByRootWindow(context->GetRootWindow(),
+                                          gfx::Rect());
+  }
   window_->layer()->SetMasksToBounds(true);
   window_->SetName("WebContentsViewAura");
 
   window_observer_.reset(new WindowObserver(this));
 
   // delegate_->GetDragDestDelegate() creates a new delegate on every call.
   // Hence, we save a reference to it locally. Similar model is used on other
   // platforms as well.
   if (delegate_.get())
     drag_dest_delegate_ = delegate_->GetDragDestDelegate();
@@ skipping 471 matching lines @@
       event.location(),
       gfx::Screen::GetScreenFor(GetNativeView())->GetCursorScreenPoint(),
       ConvertAuraEventFlagsToWebInputEventModifiers(event.flags()));
   if (drag_dest_delegate_)
     drag_dest_delegate_->OnDrop();
   current_drop_data_.reset();
   return current_drag_op_;
 }
 
 }  // namespace content