Work on flexible mode and screen sharing.

webrtc/modules/video_coding/main/source/decoding_state.h

Index: webrtc/modules/video_coding/main/source/decoding_state.h
diff --git a/webrtc/modules/video_coding/main/source/decoding_state.h b/webrtc/modules/video_coding/main/source/decoding_state.h
index 99ee33519530fa78d431ed3ff43a38e360af4c39..fe40b24030b3cfcc2f3e613565e6df906c191eee 100644
--- a/webrtc/modules/video_coding/main/source/decoding_state.h
+++ b/webrtc/modules/video_coding/main/source/decoding_state.h
@@ -21,6 +21,11 @@ class VCMPacket;
 
 class VCMDecodingState {
  public:
+  // The max number of bits used to reference back
+  // to a previous frame when using flexible mode.
+  static const uint16_t kNumRefBits = 7;
+  static const uint16_t kFrameDecodedLength = 1 << kNumRefBits;
+
   VCMDecodingState();
   ~VCMDecodingState();
   // Check for old frame
@@ -52,7 +57,10 @@ class VCMDecodingState {
   bool ContinuousPictureId(int picture_id) const;
   bool ContinuousSeqNum(uint16_t seq_num) const;
   bool ContinuousLayer(int temporal_id, int tl0_pic_id) const;
+  bool ContinuousFrameRefs(const VCMFrameBuffer* frame) const;
   bool UsingPictureId(const VCMFrameBuffer* frame) const;
+  bool UsingFlexibleMode(const VCMFrameBuffer* frame) const;
+  bool AheadOfFramesDecodedClearedTo(uint16_t index) const;
 
   // Keep state of last decoded frame.
   // TODO(mikhal/stefan): create designated classes to handle these types.
@@ -63,6 +71,10 @@ class VCMDecodingState {
   int         tl0_pic_id_;
   bool        full_sync_;  // Sync flag when temporal layers are used.
   bool        in_initial_state_;
+
+  // Used to check references in flexible mode.
+  bool frame_decoded_[kFrameDecodedLength];
+  uint16_t frame_decoded_cleared_to_;
 };
 
 }  // namespace webrtc