Don't set the screenshare flag on FakeVideoCapturerWithTaskQueue

A capturer with this flag was set in
WebRtcVideoChannelTest.PreviousAdaptationDoesNotApplyToScreenshare.
But the flag is used only by the VideoCapturerTrackSource class, which
isn't used in this test.

Bug: webrtc:6353
Change-Id: I58058c882c5a65b5cfa9921e302c422c8ccb20a9
Reviewed-on: https://webrtc-review.googlesource.com/c/117561
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26256}
diff --git a/media/engine/webrtc_video_engine_unittest.cc b/media/engine/webrtc_video_engine_unittest.cc
index 7ba9ae8..0ad396e 100644
--- a/media/engine/webrtc_video_engine_unittest.cc
+++ b/media/engine/webrtc_video_engine_unittest.cc
@@ -3375,13 +3375,10 @@
   EXPECT_EQ(720 * 3 / 4, send_stream->GetLastHeight());
 
   // Switch to screen share. Expect no CPU adaptation.
-  FakeVideoCapturerWithTaskQueue screen_share(true);
-  ASSERT_EQ(cricket::CS_RUNNING,
-            screen_share.Start(screen_share.GetSupportedFormats()->front()));
   cricket::VideoOptions screenshare_options;
   screenshare_options.is_screencast = true;
-  channel_->SetVideoSend(last_ssrc_, &screenshare_options, &screen_share);
-  EXPECT_TRUE(screen_share.CaptureCustomFrame(1284, 724));
+  channel_->SetVideoSend(last_ssrc_, &screenshare_options, &capturer);
+  EXPECT_TRUE(capturer.CaptureCustomFrame(1284, 724));
   ASSERT_EQ(2, fake_call_->GetNumCreatedSendStreams());
   send_stream = fake_call_->GetVideoSendStreams().front();
   EXPECT_EQ(1, send_stream->GetNumberOfSwappedFrames());