[DesktopCapturer] FallbackDesktopCapturerWrapper and its tests

webrtc/modules/desktop_capture/BUILD.gn

Index: webrtc/modules/desktop_capture/BUILD.gn
diff --git a/webrtc/modules/desktop_capture/BUILD.gn b/webrtc/modules/desktop_capture/BUILD.gn
index 6e7e9bcf3971c946b4383a23db01848ae35678ae..5b10a4d7696e8676e7867b8411e15c3e7b54d4d4 100644
--- a/webrtc/modules/desktop_capture/BUILD.gn
+++ b/webrtc/modules/desktop_capture/BUILD.gn
@@ -63,6 +63,7 @@ if (rtc_include_tests) {
       "desktop_frame_rotation_unittest.cc",
       "desktop_region_unittest.cc",
       "differ_block_unittest.cc",
+      "fallback_desktop_capturer_wrapper_unittest.cc",
       "mouse_cursor_monitor_unittest.cc",
       "rgba_color_unittest.cc",
       "test_utils.cc",
@@ -185,6 +186,8 @@ rtc_static_library("desktop_capture") {
     "desktop_frame_win.h",
     "differ_block.cc",
     "differ_block.h",
+    "fallback_desktop_capturer_wrapper.cc",
+    "fallback_desktop_capturer_wrapper.h",
     "mac/desktop_configuration.h",
     "mac/desktop_configuration.mm",
     "mac/desktop_configuration_monitor.cc",
@@ -281,6 +284,7 @@ rtc_static_library("desktop_capture") {
   deps = [
     ":primitives",
     "../..:webrtc_common",
+    "../../base:gtest_prod",
     "../../base:rtc_base",  # TODO(kjellander): Cleanup in bugs.webrtc.org/3806.
     "../../system_wrappers",
     "//third_party/libyuv",