WIP: Add Firefox interop tests for different formats.

chrome/browser/media/webrtc/webrtc_browsertest_base.cc

Index: chrome/browser/media/webrtc/webrtc_browsertest_base.cc
diff --git a/chrome/browser/media/webrtc/webrtc_browsertest_base.cc b/chrome/browser/media/webrtc/webrtc_browsertest_base.cc
index 1d76576bbd0ad7562172c7f5d6b7ed95eda0afe5..a80bc923ecedd55a8812274508754104f5d4eaf2 100644
--- a/chrome/browser/media/webrtc/webrtc_browsertest_base.cc
+++ b/chrome/browser/media/webrtc/webrtc_browsertest_base.cc
@@ -459,6 +459,13 @@ bool WebRtcTestBase::WaitForVideoToPlay(
   return is_video_playing;
 }
 
+void WebRtcTestBase::CheckVideoFormat(content::WebContents* tab_contents,
+                                      std::string const& format) const {
+  std::string javascript =
+      base::StringPrintf("checkVideoFormat('%s')", format.c_str());
+  EXPECT_EQ("ok-correct-format", ExecuteJavascript(javascript, tab_contents));
+}
+
 std::string WebRtcTestBase::GetStreamSize(
     content::WebContents* tab_contents,
     const std::string& video_element) const {