Add a new control of golden frame boost in CBR mode

0 means that golden boost is off, and uses average frame target rate,
a non-zero number means the percentage of boost over average frame
bitrate is given initially to golden frames in CBR mode.

Change-Id: If4334fe2cc424b65ae0cce27f71b5561bf1e577d

vpx/vp8cx.h

diff --git a/vpx/vp8cx.h b/vpx/vp8cx.h
index 406a0d2..67e00fb 100644
--- a/vpx/vp8cx.h
+++ b/vpx/vp8cx.h
@@ -208,6 +208,19 @@
    */
   VP8E_SET_MAX_INTER_BITRATE_PCT,
 
+  /*!\brief Boost percentage for Golden Frame in CBR mode
+   *
+   * This value controls the amount of boost given to Golden Frame in
+   * CBR mode. It is expressed as a percentage of the average
+   * per-frame bitrate, with the special (and default) value 0 meaning
+   * the feature is off, i.e., no golden frame boost in CBR mode and
+   * average bitrate target is used.
+   *
+   * For example, to allow 100% more bits, i.e, 2X, in a golden frame
+   * than average frame, set this to 100.
+   *
+   */
+  VP8E_SET_GF_CBR_BOOST_PCT,
 
   /* TODO(jkoleszar): Move to vp9cx.h */
   VP9E_SET_LOSSLESS,
@@ -376,6 +389,7 @@
 VPX_CTRL_USE_TYPE(VP8E_SET_MAX_INTRA_BITRATE_PCT, unsigned int)
 VPX_CTRL_USE_TYPE(VP8E_SET_MAX_INTER_BITRATE_PCT, unsigned int)
 
+VPX_CTRL_USE_TYPE(VP8E_SET_GF_CBR_BOOST_PCT, unsigned int)
 VPX_CTRL_USE_TYPE(VP9E_SET_LOSSLESS, unsigned int)
 
 VPX_CTRL_USE_TYPE(VP9E_SET_FRAME_PARALLEL_DECODING, unsigned int)