Re-add kUseGpuInTests flag in WebRTC browser tests.

chrome/browser/media/chrome_webrtc_simulcast_browsertest.cc

Index: chrome/browser/media/chrome_webrtc_simulcast_browsertest.cc
diff --git a/chrome/browser/media/chrome_webrtc_simulcast_browsertest.cc b/chrome/browser/media/chrome_webrtc_simulcast_browsertest.cc
index 329440c0ab48f68d857baa9ae800f265f2856420..8b69d44c3e98a86f27badfd25ff5f64773fadc13 100644
--- a/chrome/browser/media/chrome_webrtc_simulcast_browsertest.cc
+++ b/chrome/browser/media/chrome_webrtc_simulcast_browsertest.cc
@@ -33,6 +33,9 @@ class WebRtcSimulcastBrowserTest : public WebRtcTestBase {
     // Just answer 'allow' to GetUserMedia invocations.
     command_line->AppendSwitch(switches::kUseFakeUIForMediaStream);
 
+    // The video playback will not work without a GPU, so force its use here.
+    command_line->AppendSwitch(switches::kUseGpuInTests);
+
     // Use fake devices in order to run on VMs.
     command_line->AppendSwitch(switches::kUseFakeDeviceForMediaStream);
   }