Removed the ProcessingComponent class

BUG=

Review URL: https://codereview.webrtc.org/1772553002

Cr-Commit-Position: refs/heads/master@{#11950}
diff --git a/webrtc/modules/audio_processing/gain_control_impl.h b/webrtc/modules/audio_processing/gain_control_impl.h
index 54b8ea7..b5fe1e3 100644
--- a/webrtc/modules/audio_processing/gain_control_impl.h
+++ b/webrtc/modules/audio_processing/gain_control_impl.h
@@ -19,7 +19,7 @@
 #include "webrtc/base/thread_annotations.h"
 #include "webrtc/common_audio/swap_queue.h"
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
-#include "webrtc/modules/audio_processing/processing_component.h"
+#include "webrtc/modules/audio_processing/render_queue_item_verifier.h"
 
 namespace webrtc {