Include event_wrapper.h only where used.

It's currently used only by the VCMJitterBuffer and VCMReceiver
classes. Injection is needed by the VCMReceiverTimingTest test, which
defines a subclass(!) of EventWrapper.

Bug: webrtc:3380
Change-Id: I765be0ceac58e941928319cc426ba49f1cbdc5fa
Reviewed-on: https://webrtc-review.googlesource.com/c/113002
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25893}

modules/video_coding/include/video_coding.h

@@ -18,7 +18,6 @@
 #include "modules/include/module_common_types.h"
 #include "modules/video_coding/include/video_coding_defines.h"
 #include "rtc_base/deprecation.h"
-#include "system_wrappers/include/event_wrapper.h"
 
 namespace webrtc {
 

modules/video_coding/jitter_buffer.cc

@@ -28,7 +28,6 @@
 #include "rtc_base/system/fallthrough.h"
 #include "rtc_base/trace_event.h"
 #include "system_wrappers/include/clock.h"
-#include "system_wrappers/include/event_wrapper.h"
 #include "system_wrappers/include/field_trial.h"
 #include "system_wrappers/include/metrics.h"
 

modules/video_coding/jitter_buffer.h

@@ -28,6 +28,7 @@
 #include "rtc_base/constructormagic.h"
 #include "rtc_base/criticalsection.h"
 #include "rtc_base/thread_annotations.h"
+#include "system_wrappers/include/event_wrapper.h"
 
 namespace webrtc {
 
@@ -35,7 +36,6 @@ enum VCMNackMode { kNack, kNoNack };
 
 // forward declarations
 class Clock;
-class EventWrapper;
 class VCMFrameBuffer;
 class VCMPacket;
 class VCMEncodedFrame;

modules/video_coding/receiver.h

@@ -20,6 +20,7 @@
 #include "modules/video_coding/packet.h"
 #include "modules/video_coding/timing.h"
 #include "rtc_base/criticalsection.h"
+#include "system_wrappers/include/event_wrapper.h"
 
 namespace webrtc {