Reland of "Adds a WebRTC browser_test with opus dtx enabled.".

chrome/browser/media/webrtc_browsertest_base.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_MEDIA_WEBRTC_BROWSERTEST_BASE_H_
 #define CHROME_BROWSER_MEDIA_WEBRTC_BROWSERTEST_BASE_H_
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 111 matching lines @@
       content::WebContents* tab,
       const std::string& certificate) const;
 
   // Exchanges offers and answers between the peer connections in the
   // respective tabs. Before calling this, you must have prepared peer
   // connections in both tabs and configured them as you like (for instance by
   // calling SetupPeerconnectionWithLocalStream).
   // 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;
 
   // Hangs up a negotiated call.
   void HangUp(content::WebContents* from_tab) const;
 
   // Call this to enable monitoring of javascript errors for this test method.
   // This will only work if the tests are run sequentially by the test runner
   // (i.e. with --test-launcher-developer-mode or --test-launcher-jobs=1).
   void DetectErrorsInJavaScript();
 
   // Methods for detecting if video is playing (the loaded page must have
@@ skipping 15 matching lines @@
 
   void OpenDatabase(content::WebContents* tab) const;
   void CloseDatabase(content::WebContents* tab) const;
   void DeleteDatabase(content::WebContents* tab) const;
 
   void GenerateAndCloneCertificate(content::WebContents* tab,
                                    const std::string& keygen_algorithm) const;
 
   void VerifyStatsGenerated(content::WebContents* tab) const;
 
+  // Change the default video codec in the offer SDP.
+  void SetDefaultVideoCodec(content::WebContents* tab,
+                            const std::string& video_codec) const;
+
+  // Add 'usedtx=1' to the offer SDP.
+  void EnableOpusDtx(content::WebContents* tab) const;
+
  private:
   void CloseInfoBarInTab(content::WebContents* tab_contents,
                          infobars::InfoBar* infobar) const;
 
-  std::string CreateLocalOffer(
-      content::WebContents* from_tab,
-      std::string default_video_codec = kUseDefaultVideoCodec) const;
-  std::string CreateAnswer(
-      std::string local_offer,
-      content::WebContents* to_tab,
-      std::string default_video_codec = kUseDefaultVideoCodec) const;
+  std::string CreateLocalOffer(content::WebContents* from_tab) const;
+  std::string CreateAnswer(std::string local_offer,
+                           content::WebContents* to_tab) const;
   void ReceiveAnswer(const std::string& answer,
                      content::WebContents* from_tab) const;
   void GatherAndSendIceCandidates(content::WebContents* from_tab,
                                   content::WebContents* to_tab) const;
 
   infobars::InfoBar* GetUserMediaAndWaitForInfoBar(
       content::WebContents* tab_contents,
       const std::string& constraints) const;
 
   bool detect_errors_in_javascript_;
 
   DISALLOW_COPY_AND_ASSIGN(WebRtcTestBase);
 };
 
 #endif  // CHROME_BROWSER_MEDIA_WEBRTC_BROWSERTEST_BASE_H_