Adds a WebRTC browser_test with opus dtx enabled.

chrome/browser/media/webrtc_browsertest_base.h

Index: chrome/browser/media/webrtc_browsertest_base.h
diff --git a/chrome/browser/media/webrtc_browsertest_base.h b/chrome/browser/media/webrtc_browsertest_base.h
index 68fd0e717655f10c41d811210f69385e325bccb9..85eaeac1d8f4c3f69964375b0f44401ffdbaf6e0 100644
--- a/chrome/browser/media/webrtc_browsertest_base.h
+++ b/chrome/browser/media/webrtc_browsertest_base.h
@@ -129,10 +129,10 @@ class WebRtcTestBase : public InProcessBrowserTest {
   // If |video_codec| is not |kUseDefaultVideoCodec|, the SDP offer is modified
   // (and SDP answer verified) so that the specified video codec (case-sensitive
   // name) is used during the call instead of the default one.
-  void NegotiateCall(
-      content::WebContents* from_tab,
-      content::WebContents* to_tab,
-      const std::string& video_codec = kUseDefaultVideoCodec) const;
+  void NegotiateCall(content::WebContents* from_tab,
+                     content::WebContents* to_tab,
+                     const std::string& video_codec = kUseDefaultVideoCodec,
+                     bool opus_dtx = false) const;
 
   // Hangs up a negotiated call.
   void HangUp(content::WebContents* from_tab) const;
@@ -172,11 +172,13 @@ class WebRtcTestBase : public InProcessBrowserTest {
 
   std::string CreateLocalOffer(
       content::WebContents* from_tab,
-      std::string default_video_codec = kUseDefaultVideoCodec) const;
+      std::string default_video_codec = kUseDefaultVideoCodec,
+      bool opus_dtx = false) const;
   std::string CreateAnswer(
       std::string local_offer,
       content::WebContents* to_tab,
-      std::string default_video_codec = kUseDefaultVideoCodec) const;
+      std::string default_video_codec = kUseDefaultVideoCodec,
+      bool opus_dtx = false) const;
   void ReceiveAnswer(const std::string& answer,
                      content::WebContents* from_tab) const;
   void GatherAndSendIceCandidates(content::WebContents* from_tab,