Clean up WebRTC related includes files in content.

content/renderer/renderer_blink_platform_impl.cc

Index: content/renderer/renderer_blink_platform_impl.cc
diff --git a/content/renderer/renderer_blink_platform_impl.cc b/content/renderer/renderer_blink_platform_impl.cc
index a88006743f7c36a315aac5e1400c58cfb374573a..212a9ec7dc2af291e0c7bac2dc2ad23a51cb1a8a 100644
--- a/content/renderer/renderer_blink_platform_impl.cc
+++ b/content/renderer/renderer_blink_platform_impl.cc
@@ -63,7 +63,6 @@
 #include "content/renderer/media/media_recorder_handler.h"
 #include "content/renderer/media/renderer_webaudiodevice_impl.h"
 #include "content/renderer/media/renderer_webmidiaccessor_impl.h"
-#include "content/renderer/media/rtc_certificate_generator.h"
 #include "content/renderer/mojo/blink_interface_provider_impl.h"
 #include "content/renderer/render_thread_impl.h"
 #include "content/renderer/renderer_clipboard_delegate.h"
@@ -137,6 +136,7 @@
 #endif
 
 #if defined(ENABLE_WEBRTC)
+#include "content/renderer/media/rtc_certificate_generator.h"
 #include "content/renderer/media/webrtc/peer_connection_dependency_factory.h"
 #endif