AudioProcessingModule has a feature to make a recording of its
configuration, inputs and outputs over a period of time. It is
activated by AudioProcessing::StartRecording. The data is stored in
binary protobuf format in a specified file. The file IO is, as of
this CL, done from the real-time audio thread.

This CL contains an interface for AecDump, a new APM submodule that
will handle the recordings. Calls to the new interface from the
AudioProcessingModule are added. These calls have no effect, and for a
short while, audio_processing_impl.cc will contain two copies of
recording calls.

The original calls are guarded by the WEBRTC_AUDIOPROC_DEBUG_DUMP
preprocessor define. They still have an effect, while the new ones do
not. In the following CLs, the old recording calls will be removed,
and an implementation of AecDump added.

The reasons for the refactoring is to move file IO operations from the
real-time audio thread, to add a top-level low-priority task queue for
logging tasks like this, to simplify and modularize audio_processing_impl.cc
and remove some of the preprocessor directives. These goals will be
archived by the upcoming CLs. The implementation is in
https://codereview.webrtc.org/2865113002.

BUG=webrtc:7404

Review-Url: https://codereview.webrtc.org/2778783002
Cr-Commit-Position: refs/heads/master@{#18233}
diff --git a/webrtc/modules/audio_processing/include/audio_processing.cc b/webrtc/modules/audio_processing/include/audio_processing.cc
index 9a3b84d..eec4db6 100644
--- a/webrtc/modules/audio_processing/include/audio_processing.cc
+++ b/webrtc/modules/audio_processing/include/audio_processing.cc
@@ -10,6 +10,11 @@
 
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
 
+#include "webrtc/base/checks.h"
+#include "webrtc/modules/audio_processing/include/aec_dump.h"
+// TODO(aleloi): remove AecDump header usage when internal projcets
+// have updated. See https://bugs.webrtc.org/7404.
+
 namespace webrtc {
 
 Beamforming::Beamforming()
@@ -31,4 +36,20 @@
 
 Beamforming::~Beamforming() {}
 
+// TODO(aleloi): make pure virtual when internal projects have
+// updated. See https://bugs.webrtc.org/7404
+void AudioProcessing::AttachAecDump(std::unique_ptr<AecDump> aec_dump) {
+  RTC_NOTREACHED();
+}
+
+// If no AecDump is attached, this has no effect. If an AecDump is
+// attached, it's destructor is called. The d-tor may block until
+// all pending logging tasks are completed.
+//
+// TODO(aleloi): make pure virtual when internal projects have
+// updated. See https://bugs.webrtc.org/7404
+void AudioProcessing::DetachAecDump() {
+  RTC_NOTREACHED();
+}
+
 }  // namespace webrtc