Reland "Fix about:webrtc-internals "Stats Tables""

This reverts commit 2302c7e1.

Reason for revert: relanding because without win-build-perf is broken (possibly needs manual work).

Original change's description:
> Revert "Fix about:webrtc-internals "Stats Tables""
> 
> This reverts commit f61878bc.
> 
> Reason for revert: [sheriff] it looks very likely that this change caused a crash in WebRTCInternalsIntegrationBrowserTest.IntegrationWithWebRtcEventLogger (https://ci.chromium.org/p/chromium/builders/ci/Mac10.10%20Tests/48280).
> 
> Original change's description:
> > Fix about:webrtc-internals "Stats Tables"
> > 
> > This is a fixup CL of [1] spotted and report by hbos@chromium.org
> > on [2].
> > 
> > [1] https://crrev.com/c/1842414 (Onion soup RTCPeerConnectionHandler and its direct dependences)
> > [2] https://crrev.com/c/1842414/14#message-daf2b117b98895c3692a635ac873e249e6f905c1
> > 
> > Basically the original CL was supposed to replace the code
> > that used to bound PeerConnectionTracker to its associated
> > mojom::Receiver instance in [3] by the corresponding code in
> > Blink.
> > However, the replacement code got accidentally missing while rebasing
> > the CL over and over.
> > 
> > [3] https://crrev.com/c/1842414/14/content/renderer/render_thread_impl.cc#b777
> > 
> > This CL amends the original CL with the proper code in
> > blink/renderer/modules/modules_initializer.cc@RegisterInterfaces().
> > 
> > TEST=<out>/browser_tests --gtest_filter=WebRtcInternalsPerfBrowserTest.MANUAL_RunsAudioVideoCall60SecsAndLogsInternalMetricsVp8 \
> > --run-manual --ui-test-action-max-timeout=100000 --test-launcher-timeout=100001
> > 
> > Manual test= Open Chromium load about:webrtc-internals and [4].
> > It is expected that WebRTC statistics appear.
> > 
> > [4] https://codepen.io/anon/pen/JQLEqR?editors=1010
> > 
> > R=​haraken@chromium.org
> > TBR=guidou@chromium.org, hbos@chromium.org
> > 
> > BUG=787254
> > 
> > Change-Id: I88f26b8cbcc09b707f6db5c9e7ba40bdbd8e82e8
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1893293
> > Reviewed-by: Kentaro Hara <haraken@chromium.org>
> > Reviewed-by: Henrik Boström <hbos@chromium.org>
> > Reviewed-by: Antonio Gomes <tonikitoo@igalia.com>
> > Commit-Queue: Henrik Boström <hbos@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#711647}
> 
> TBR=haraken@chromium.org,hbos@chromium.org,guidou@chromium.org,tonikitoo@igalia.com
> 
> Change-Id: If20ddd5622f30af1bfe1a8ca7d3b041b605bc7b2
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 787254
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1895195
> Reviewed-by: Armando Miraglia <armax@chromium.org>
> Commit-Queue: Armando Miraglia <armax@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#711665}

TBR=haraken@chromium.org,hbos@chromium.org,guidou@chromium.org,tonikitoo@igalia.com,armax@chromium.org

Change-Id: I4bac5da3cae4161f788ac0d1ef602bccb1419da7
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 787254
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1893868Reviewed-by: Armando Miraglia <armax@chromium.org>
Commit-Queue: Armando Miraglia <armax@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711668}

third_party/blink/renderer/modules/modules_initializer.cc

@@ -62,6 +62,7 @@
 #include "third_party/blink/renderer/modules/media_controls/media_controls_impl.h"
 #include "third_party/blink/renderer/modules/mediastream/user_media_client.h"
 #include "third_party/blink/renderer/modules/mediastream/user_media_controller.h"
+#include "third_party/blink/renderer/modules/peerconnection/peer_connection_tracker.h"
 #include "third_party/blink/renderer/modules/picture_in_picture/picture_in_picture_controller_impl.h"
 #include "third_party/blink/renderer/modules/presentation/presentation_controller.h"
 #include "third_party/blink/renderer/modules/presentation/presentation_receiver.h"
@@ -316,6 +317,11 @@ void ModulesInitializer::RegisterInterfaces(
   registry.AddInterface(
       ConvertToBaseCallback(CrossThreadBindRepeating(&WebDatabaseImpl::Create)),
       Platform::Current()->GetIOTaskRunner());
+  registry.AddInterface(
+      ConvertToBaseCallback(CrossThreadBindRepeating(
+          &PeerConnectionTracker::Bind,
+          WTF::CrossThreadUnretained(PeerConnectionTracker::GetInstance()))),
+      Thread::MainThread()->GetTaskRunner());
 }
 
 }  // namespace blink