Export symbols needed by the Chromium component build (part 1).

This CL uses RTC_EXPORT (defined in rtc_base/system/rtc_export.h)
to mark WebRTC symbols as visible from a shared library, this doesn't
mean these symbols are part of the public API (please continue to refer
to [1] for info about what is considered public WebRTC API).

[1] - https://webrtc.googlesource.com/src/+/HEAD/native-api.md

Bug: webrtc:9419
Change-Id: I802abd32874d42d3aa5ecd3c8022e7cf5e043d99
Reviewed-on: https://webrtc-review.googlesource.com/c/103505
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24969}
diff --git a/modules/audio_processing/include/audio_processing.h b/modules/audio_processing/include/audio_processing.h
index 9d0c65e..868a66f 100644
--- a/modules/audio_processing/include/audio_processing.h
+++ b/modules/audio_processing/include/audio_processing.h
@@ -34,6 +34,7 @@
 #include "rtc_base/platform_file.h"
 #include "rtc_base/refcount.h"
 #include "rtc_base/scoped_ref_ptr.h"
+#include "rtc_base/system/rtc_export.h"
 
 namespace webrtc {
 
@@ -554,7 +555,7 @@
     float minimum_ = 0.0f;  // Long-term minimum.
   };
 
-  struct AudioProcessingStatistics {
+  struct RTC_EXPORT AudioProcessingStatistics {
     AudioProcessingStatistics();
     AudioProcessingStatistics(const AudioProcessingStatistics& other);
     ~AudioProcessingStatistics();
@@ -653,7 +654,7 @@
   static const int kChunkSizeMs = 10;
 };
 
-class AudioProcessingBuilder {
+class RTC_EXPORT AudioProcessingBuilder {
  public:
   AudioProcessingBuilder();
   ~AudioProcessingBuilder();