libvpx: Add VP9 decoder.

source/libvpx/test/datarate_test.cc

Index: source/libvpx/test/datarate_test.cc
===================================================================
--- source/libvpx/test/datarate_test.cc	(revision 172621)
+++ source/libvpx/test/datarate_test.cc	(working copy)
@@ -59,13 +59,9 @@
     /* Test the buffer model here before subtracting the frame. Do so because
      * the way the leaky bucket model works in libvpx is to allow the buffer to
      * empty - and then stop showing frames until we've got enough bits to
-     * show one. As noted in comment below (issue 495), this does not currently
-     * apply to key frames. For now exclude key frames in condition below. */
-    bool key_frame = (pkt->data.frame.flags & VPX_FRAME_IS_KEY) ? true: false;
-    if (!key_frame) {
-      ASSERT_GE(bits_in_buffer_model_, 0) << "Buffer Underrun at frame "
-          << pkt->data.frame.pts;
-    }
+     * show one. */
+    ASSERT_GE(bits_in_buffer_model_, 0) << "Buffer Underrun at frame "
+        << pkt->data.frame.pts;
 
     const int frame_size_in_bits = pkt->data.frame.sz * 8;
 
@@ -129,12 +125,7 @@
   ::libvpx_test::I420VideoSource video("hantro_collage_w352h288.yuv", 352, 288,
                                        30, 1, 0, 140);
 
-  // There is an issue for low bitrates in real-time mode, where the
-  // effective_datarate slightly overshoots the target bitrate.
-  // This is same the issue as noted about (#495).
-  // TODO(jimbankoski/marpan): Update test to run for lower bitrates (< 100),
-  // when the issue is resolved.
-  for (int i = 100; i < 800; i += 200) {
+  for (int i = 70; i < 700; i += 200) {
     cfg_.rc_target_bitrate = i;
     ResetModel();
     ASSERT_NO_FATAL_FAILURE(RunLoop(&video));