Remove RenderThread use of MediaStreamTrackMetrics

The use seems pointless now that the class uses Mojo for IPC.

This CL prepares to Onion souping this class.

BUG=787254
R=guidou@chromium.org

Change-Id: If36a51b8ff724d6a70aecc884f296e594d3fd2a9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1834362
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702027}

content/renderer/media/webrtc/media_stream_track_metrics.cc

@@ -10,7 +10,6 @@
 #include "base/hash/md5.h"
 #include "base/strings/stringprintf.h"
 #include "base/threading/thread_checker.h"
-#include "content/renderer/render_thread_impl.h"
 #include "third_party/blink/public/common/thread_safe_browser_interface_broker_proxy.h"
 #include "third_party/blink/public/platform/platform.h"
 
@@ -214,10 +213,6 @@ void MediaStreamTrackMetrics::SendLifetimeMessage(const std::string& track_id,
                                                   Kind kind,
                                                   LifetimeEvent event,
                                                   Direction direction) {
-  RenderThreadImpl* render_thread = RenderThreadImpl::current();
-  // |render_thread| can be NULL in certain cases when running as part
-  // |of a unit test.
-  if (render_thread) {
   if (event == LifetimeEvent::kConnected) {
     GetMediaStreamTrackMetricsHost()->AddTrack(
         MakeUniqueId(track_id, direction), kind == Kind::kAudio,
@@ -227,7 +222,6 @@ void MediaStreamTrackMetrics::SendLifetimeMessage(const std::string& track_id,
     GetMediaStreamTrackMetricsHost()->RemoveTrack(
         MakeUniqueId(track_id, direction));
   }
-  }
 }
 
 uint64_t MediaStreamTrackMetrics::MakeUniqueIdImpl(uint64_t pc_id,