Fix -Wformat error in Win-Clang build

webrtc/base/event_tracer.cc

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 #include "webrtc/base/event_tracer.h"
@@ skipping 103 matching lines @@
       }
       for (const TraceEvent& e : events) {
         fprintf(output_file_,
                 "%s{ \"name\": \"%s\""
                 ", \"cat\": \"%s\""
                 ", \"ph\": \"%c\""
                 ", \"ts\": %" PRIu64
                 ", \"pid\": %d"
                 ", \"tid\": %d}\n",
                 has_logged_event ? "," : " ", e.name, e.category_enabled,
-                e.phase, e.timestamp, e.pid, e.tid);
+                e.phase, e.timestamp, static_cast<int>(e.pid), e.tid);
         has_logged_event = true;
       }
       if (shutting_down)
         break;
     }
     fprintf(output_file_, "]}\n");
     if (output_file_owned_)
       fclose(output_file_);
     output_file_ = nullptr;
   }
@@ skipping 121 matching lines @@
   RTC_DCHECK(old_logger);
   RTC_CHECK(rtc::AtomicOps::CompareAndSwapPtr(
                 &g_event_logger, old_logger,
                 static_cast<EventLogger*>(nullptr)) == old_logger);
   delete old_logger;
   webrtc::SetupEventTracer(nullptr, nullptr);
 }
 
 }  // namespace tracing
 }  // namespace rtc