Fix a crash when chooseDesktopMedia is called with no target tab

chrome/browser/ui/views/desktop_media_picker_views.cc

 // Copyright 2013 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 "chrome/browser/media/desktop_media_picker.h"
 
 #include "base/callback.h"
 #include "chrome/browser/media/desktop_media_list.h"
 #include "chrome/browser/media/desktop_media_list_observer.h"
 #include "chrome/browser/ui/ash/ash_util.h"
@@ skipping 500 matching lines @@
     label_->SetText(l10n_util::GetStringFUTF16(
         IDS_DESKTOP_MEDIA_PICKER_TEXT_DELEGATED, app_name, target_name));
   }
   label_->SetMultiLine(true);
   label_->SetHorizontalAlignment(gfx::ALIGN_LEFT);
   AddChildView(label_);
 
   scroll_view_->SetContents(list_view_);
   AddChildView(scroll_view_);
 
-  WebContentsModalDialogManager* web_contents_modal_dialog_manager =
-      WebContentsModalDialogManager::FromWebContents(parent_web_contents);
-  DCHECK(web_contents_modal_dialog_manager);
-  WebContentsModalDialogManagerDelegate* delegate =
-      web_contents_modal_dialog_manager->delegate();
-  DCHECK(delegate);
-  views::Widget::CreateWindowAsFramelessChild(
-      this,
-      delegate->GetWebContentsModalDialogHost()->GetHostView());
+  WebContentsModalDialogManager* web_contents_modal_dialog_manager = NULL;
+  if (parent_web_contents) {

[Sergey Ulanov, 2014/06/03 01:27:30]

nit: add comment to explain what happens here, particularly that the window is
shown differently depending on who calls the API

+    web_contents_modal_dialog_manager =
+        WebContentsModalDialogManager::FromWebContents(parent_web_contents);
+    DCHECK(web_contents_modal_dialog_manager);
+    WebContentsModalDialogManagerDelegate* delegate =
+        web_contents_modal_dialog_manager->delegate();
+    DCHECK(delegate);
+    views::Widget::CreateWindowAsFramelessChild(
+        this,
+        delegate->GetWebContentsModalDialogHost()->GetHostView());
+  } else {
+    DialogDelegate::CreateDialogWidget(this, context, parent_window);
+  }
 
   // DesktopMediaList needs to know the ID of the picker window which
   // matches the ID it gets from the OS. Depending on the OS and configuration
   // we get this ID differently.
   content::DesktopMediaID::Id dialog_window_id = 0;
 
 #if defined(USE_ASH)
   if (chrome::IsNativeWindowInAsh(GetWidget()->GetNativeWindow())) {
     dialog_window_id = content::DesktopMediaID::RegisterAuraWindow(
         GetWidget()->GetNativeWindow()).id;
   } else
 #endif
   {
     dialog_window_id = AcceleratedWidgetToDesktopMediaId(
         GetWidget()->GetNativeWindow()->GetHost()->
             GetAcceleratedWidget());
   }
 
   list_view_->StartUpdating(dialog_window_id);
 
-  web_contents_modal_dialog_manager->ShowModalDialog(
-      GetWidget()->GetNativeView());
+  if (parent_web_contents) {
+    web_contents_modal_dialog_manager->ShowModalDialog(
+        GetWidget()->GetNativeView());
+  } else {
+    GetWidget()->Show();
+  }
 }
 
 DesktopMediaPickerDialogView::~DesktopMediaPickerDialogView() {}
 
 void DesktopMediaPickerDialogView::DetachParent() {
   parent_ = NULL;
 }
 
 gfx::Size DesktopMediaPickerDialogView::GetPreferredSize() const {
   return gfx::Size(600, 500);
@@ skipping 102 matching lines @@
       base::Bind(callback_, source));
   callback_.Reset();
 }
 
 }  // namespace
 
 // static
 scoped_ptr<DesktopMediaPicker> DesktopMediaPicker::Create() {
   return scoped_ptr<DesktopMediaPicker>(new DesktopMediaPickerViews());
 }