Add ability to scale to arbitrary factors

webrtc/media/base/videoadapter.h

Index: webrtc/media/base/videoadapter.h
diff --git a/webrtc/media/base/videoadapter.h b/webrtc/media/base/videoadapter.h
index 9d17f5ce1538f5446546f39bee1c391cc7a8f438..9ea649df25e46dc99a0d34dc570515f1fe3cb58f 100644
--- a/webrtc/media/base/videoadapter.h
+++ b/webrtc/media/base/videoadapter.h
@@ -25,6 +25,7 @@ namespace cricket {
 class VideoAdapter {
  public:
   VideoAdapter();
+  VideoAdapter(int required_resolution_alignment);
   virtual ~VideoAdapter();
 
   // Return the adapted resolution and cropping parameters given the
@@ -63,6 +64,8 @@ class VideoAdapter {
   int adaption_changes_;  // Number of changes in scale factor.
   int previous_width_;    // Previous adapter output width.
   int previous_height_;   // Previous adapter output height.
+  // Resolution must be divisible by this factor.
+  const int required_resolution_alignment_;
   // The target timestamp for the next frame based on requested format.
   rtc::Optional<int64_t> next_frame_timestamp_ns_ GUARDED_BY(critical_section_);