Re-add kUseGpuInTests flag in WebRTC browser tests.

chrome/browser/media/chrome_webrtc_video_quality_browsertest.cc

Index: chrome/browser/media/chrome_webrtc_video_quality_browsertest.cc
diff --git a/chrome/browser/media/chrome_webrtc_video_quality_browsertest.cc b/chrome/browser/media/chrome_webrtc_video_quality_browsertest.cc
index 6c88d9594defcdcf5216932abfa27c9e730312e1..7d1347ed9a6227b686fa8fd561e5552944f5e2b4 100644
--- a/chrome/browser/media/chrome_webrtc_video_quality_browsertest.cc
+++ b/chrome/browser/media/chrome_webrtc_video_quality_browsertest.cc
@@ -116,6 +116,9 @@ class WebRtcVideoQualityBrowserTest : public WebRtcTestBase,
     command_line->AppendSwitchPath(switches::kUseFileForFakeVideoCapture,
                                    webrtc_reference_video_y4m_);
     command_line->AppendSwitch(switches::kUseFakeDeviceForMediaStream);
+
+    // The video playback will not work without a GPU, so force its use here.
+    command_line->AppendSwitch(switches::kUseGpuInTests);
   }
 
   // Writes all frames we've captured so far by grabbing them from the