[adaptation] Expose target pixels and max framerate in VideoAdapter

This will enable wiring up these signals to the platform specific capturers

Bug: chromium:1116430
Change-Id: I6cdab61eab202a24fa56167da57c389a5b1880c2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/182683
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32017}

media/base/video_adapter.cc

@@ -349,4 +349,22 @@ void VideoAdapter::OnSinkWants(const rtc::VideoSinkWants& sink_wants) {
       source_resolution_alignment_, sink_wants.resolution_alignment);
 }
 
+int VideoAdapter::GetTargetPixels() const {
+  webrtc::MutexLock lock(&mutex_);
+  return resolution_request_target_pixel_count_;
+}
+
+float VideoAdapter::GetMaxFramerate() const {
+  webrtc::MutexLock lock(&mutex_);
+  // Minimum of |max_fps_| and |max_framerate_request_| is used to throttle
+  // frame-rate.
+  int framerate = std::min(max_framerate_request_,
+                           max_fps_.value_or(max_framerate_request_));
+  if (framerate == std::numeric_limits<int>::max()) {
+    return std::numeric_limits<float>::infinity();
+  } else {
+    return max_framerate_request_;
+  }
+}
+
 }  // namespace cricket

media/base/video_adapter.h

@@ -97,6 +97,14 @@ class VideoAdapter {
   void OnSinkWants(const rtc::VideoSinkWants& sink_wants)
       RTC_LOCKS_EXCLUDED(mutex_);
 
+  // Returns maximum image area, which shouldn't impose any adaptations.
+  // Can return |numeric_limits<int>::max()| if no limit is set.
+  int GetTargetPixels() const;
+
+  // Returns current frame-rate limit.
+  // Can return |numeric_limits<float>::infinity()| if no limit is set.
+  float GetMaxFramerate() const;
+
  private:
   // Determine if frame should be dropped based on input fps and requested fps.
   bool KeepFrame(int64_t in_timestamp_ns) RTC_EXCLUSIVE_LOCKS_REQUIRED(mutex_);
@@ -136,7 +144,7 @@ class VideoAdapter {
   int max_framerate_request_ RTC_GUARDED_BY(mutex_);
 
   // The critical section to protect the above variables.
-  webrtc::Mutex mutex_;
+  mutable webrtc::Mutex mutex_;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(VideoAdapter);
 };