Remove unused FakeClock from data_channel_integrationtest

Bug: webrtc:42223992
Change-Id: I58a66ddb4e410b4475b060e5bb661bb76a6a6964
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/462000
Auto-Submit: Evan Shrubsole <eshr@webrtc.org>
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#47348}

pc/data_channel_integrationtest.cc

diff --git a/pc/data_channel_integrationtest.cc b/pc/data_channel_integrationtest.cc
index cf7a5b7..b1ce96b 100644
--- a/pc/data_channel_integrationtest.cc
+++ b/pc/data_channel_integrationtest.cc
@@ -42,7 +42,6 @@
 #include "pc/test/mock_peer_connection_observers.h"
 #include "rtc_base/copy_on_write_buffer.h"
 #include "rtc_base/crypto_random.h"
-#include "rtc_base/fake_clock.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/numerics/safe_conversions.h"
 #include "rtc_base/socket_address.h"
@@ -104,25 +103,6 @@
   const bool allow_media_;
 };
 
-// Fake clock must be set before threads are started to prevent race on
-// Set/GetClockForTesting().
-// To achieve that, multiple inheritance is used as a mixin pattern
-// where order of construction is finely controlled.
-// This also ensures peerconnection is closed before switching back to non-fake
-// clock, avoiding other races and DCHECK failures such as in rtp_sender.cc.
-class FakeClockForTest : public ScopedFakeClock {
- protected:
-  FakeClockForTest() {
-    // Some things use a time of "0" as a special value, so we need to start out
-    // the fake clock at a nonzero time.
-    // TODO(deadbeef): Fix this.
-    AdvanceTime(TimeDelta::Seconds(1));
-  }
-
-  // Explicit handle.
-  ScopedFakeClock& FakeClock() { return *this; }
-};
-
 class DataChannelIntegrationTestPlanB
     : public PeerConnectionIntegrationBaseTest {
  protected: