Fix DesktopMediaPickerViews to handle background parent_web_contents

After r283702 DesktopMediaPickerViews is getting parent_web_contents even
when it corresponds to a background extension page.
DesktopMediaPickerViews was always trying to create a modal dialog when
web_contents is specified, and that doesn't work for background pages.
Now it explicitly checks if the web_contents is a background page and
in that case shows the picker in a separate window.

Also updated example for desktop capture API to make it easier to test
this scenario.

BUG=402579

Review URL: https://codereview.chromium.org/501713002

Cr-Commit-Position: refs/heads/master@{#292055}
(cherry picked from commit 71b32fc)

TBR=sergeyu@chromium.org

Review URL: https://codereview.chromium.org/522483007

Cr-Commit-Position: refs/branch-heads/2125@{#179}
Cr-Branched-From: b68026d-refs/heads/master@{#290040}

chrome/browser/ui/views/desktop_media_picker_views.cc

@@ -11,6 +11,7 @@
 #include "chrome/grit/generated_resources.h"
 #include "components/web_modal/popup_manager.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/web_contents_delegate.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/events/event_constants.h"
@@ -358,7 +359,6 @@ void DesktopMediaListView::OnSourceThumbnailChanged(int index) {
 DesktopMediaPickerDialogView::DesktopMediaPickerDialogView(
     content::WebContents* parent_web_contents,
     gfx::NativeWindow context,
-    gfx::NativeWindow parent_window,
     DesktopMediaPickerViews* parent,
     const base::string16& app_name,
     const base::string16& target_name,
@@ -384,26 +384,25 @@ DesktopMediaPickerDialogView::DesktopMediaPickerDialogView(
       GetMediaListViewHeightForRows(1), GetMediaListViewHeightForRows(2));
   AddChildView(scroll_view_);
 
-  // If |parent_web_contents| is set, the picker will be shown modal to the
-  // web contents. Otherwise, a new dialog widget inside |parent_window| will be
-  // created for the picker. Note that |parent_window| may also be NULL if
-  // parent web contents is not set. In this case the picker will be parented
-  // by a root window.
+  // If |parent_web_contents| is set and it's not a background page then the
+  // picker will be shown modal to the web contents. Otherwise the picker is
+  // shown in a separate window.
   views::Widget* widget = NULL;
-  if (parent_web_contents)
+  bool modal_dialog =
+      parent_web_contents &&
+      !parent_web_contents->GetDelegate()->IsNeverVisible(parent_web_contents);
+  if (modal_dialog) {
     widget = CreateWebModalDialogViews(this, parent_web_contents);
-  else
-    widget = DialogDelegate::CreateDialogWidget(this, context, parent_window);
+  } else {
+    widget = DialogDelegate::CreateDialogWidget(this, context, NULL);
+  }
 
-  // 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.
+  // If the picker is not modal to the calling web contents then it is displayed
+  // in its own top-level window, so in that case it needs to be filtered out of
+  // the list of top-level windows available for capture, and to achieve that
+  // the Id is passed to DesktopMediaList.
   DesktopMediaID::Id dialog_window_id = 0;
-
-  // If there is |parent_window| or |parent_web_contents|, the picker window
-  // is embedded in the parent and does not have its own native window id, so we
-  // do not filter in that case.
-  if (!parent_window && !parent_web_contents) {
+  if (!modal_dialog) {
 #if defined(USE_ASH)
     if (chrome::IsNativeWindowInAsh(widget->GetNativeWindow())) {
       dialog_window_id =
@@ -420,7 +419,7 @@ DesktopMediaPickerDialogView::DesktopMediaPickerDialogView(
 
   list_view_->StartUpdating(dialog_window_id);
 
-  if (parent_web_contents) {
+  if (modal_dialog) {
     web_modal::PopupManager* popup_manager =
         web_modal::PopupManager::FromWebContents(parent_web_contents);
     popup_manager->ShowModalDialog(GetWidget()->GetNativeView(),
@@ -555,8 +554,7 @@ void DesktopMediaPickerViews::Show(content::WebContents* web_contents,
                                    const DoneCallback& done_callback) {
   callback_ = done_callback;
   dialog_ = new DesktopMediaPickerDialogView(
-      web_contents, context, parent, this, app_name, target_name,
-      media_list.Pass());
+      web_contents, context, this, app_name, target_name, media_list.Pass());
 }
 
 void DesktopMediaPickerViews::NotifyDialogResult(DesktopMediaID source) {

chrome/browser/ui/views/desktop_media_picker_views.h

@@ -108,7 +108,6 @@ class DesktopMediaPickerDialogView : public views::DialogDelegateView {
  public:
   DesktopMediaPickerDialogView(content::WebContents* parent_web_contents,
                                gfx::NativeWindow context,
-                               gfx::NativeWindow parent_window,
                                DesktopMediaPickerViews* parent,
                                const base::string16& app_name,
                                const base::string16& target_name,

chrome/browser/ui/views/desktop_media_picker_views_unittest.cc

@@ -46,8 +46,8 @@ class DesktopMediaPickerViewsTest : public testing::Test {
 
     picker_views_.reset(new DesktopMediaPickerViews());
     picker_views_->Show(NULL,
-                        NULL,
                         parent_widget_->GetNativeWindow(),
+                        NULL,
                         app_name,
                         app_name,
                         media_list.PassAs<DesktopMediaList>(),

chrome/common/extensions/docs/examples/api/desktopCapture/app.js

@@ -38,3 +38,9 @@ document.querySelector('#cancel').addEventListener('click', function(e) {
     chrome.desktopCapture.cancelChooseDesktopMedia(pending_request_id);
   }
 });
+
+document.querySelector('#startFromBackgroundPage')
+    .addEventListener('click', function(e) {
+      chrome.runtime.sendMessage(
+          {}, function(response) { console.log(response.farewell); });
+    });

chrome/common/extensions/docs/examples/api/desktopCapture/background.js

@@ -10,3 +10,11 @@ chrome.app.runtime.onLaunched.addListener(function() {
     }
   });
 });
+
+chrome.runtime.onMessage.addListener(function(message, sender, sendResponse) {
+  chrome.desktopCapture.chooseDesktopMedia(
+      ["screen", "window"],
+      function(id) {
+        sendResponse({"id": id});
+      });
+});

chrome/common/extensions/docs/examples/api/desktopCapture/index.html

@@ -18,7 +18,11 @@
 </head>
 <body>
   <video id="video" autoplay></video>
-  <p><button id="start">Start</button><button id="cancel">Cancel</button></p>
+  <p>
+    <button id="start">Start</button>
+    <button id="cancel">Cancel</button>
+    <button id="startFromBackgroundPage">Start from background page</button>
+  </p>
   <script src="app.js"></script>
 </body>
 </html>