Add AshDesktopMediaList and enable Desktop Capture API on Chrome OS.

chrome/browser/extensions/api/desktop_capture/desktop_capture_api.cc

Index: chrome/browser/extensions/api/desktop_capture/desktop_capture_api.cc
diff --git a/chrome/browser/extensions/api/desktop_capture/desktop_capture_api.cc b/chrome/browser/extensions/api/desktop_capture/desktop_capture_api.cc
index 9cd24f25f06242ef0d70b9abd83c64bd403c495f..e8474e869e860a4e84f739f9ec6f9dcba4bd12dc 100644
--- a/chrome/browser/extensions/api/desktop_capture/desktop_capture_api.cc
+++ b/chrome/browser/extensions/api/desktop_capture/desktop_capture_api.cc
@@ -7,6 +7,7 @@
 #include "base/compiler_specific.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/extensions/extension_tab_util.h"
+#include "chrome/browser/media/ash_desktop_media_list.h"
 #include "chrome/browser/media/desktop_streams_registry.h"
 #include "chrome/browser/media/media_capture_devices_dispatcher.h"
 #include "chrome/browser/media/native_desktop_media_list.h"
@@ -165,7 +166,12 @@ bool DesktopCaptureChooseDesktopMediaFunction::RunImpl() {
   } else {
     // DesktopMediaPicker is implemented only for Windows, OSX and
     // Aura Linux builds.
-#if (defined(TOOLKIT_VIEWS) && !defined(OS_CHROMEOS)) || defined(OS_MACOSX)
+#if defined(USE_ASH)
+    media_list.reset(new AshDesktopMediaList(
+        (show_screens ? AshDesktopMediaList::SCREENS : 0) |
+        (show_windows ? AshDesktopMediaList::WINDOWS : 0)));
+    picker_ = DesktopMediaPicker::Create();
+#elif defined(TOOLKIT_VIEWS) || defined(OS_MACOSX)
     webrtc::DesktopCaptureOptions options =
         webrtc::DesktopCaptureOptions::CreateDefault();
     options.set_disable_effects(false);