Roll libvpx 42ddeb:55f7ba

libvpx roll:
https://codereview.chromium.org/592203002

re-instate image compatibility:
https://codereview.chromium.org/588403002

Use new VP9E_SET_NOISE_SENSITIVITY introduced in:
https://gerrit.chromium.org/gerrit/gitweb?p=webm%2Flibvpx.git;a=commit;h=bb1a23656c63097a4b250ac484b14051f09df9b5

NOTRY=true

R=tomfinegan@chromium.org

Review URL: https://codereview.chromium.org/595653003

Cr-Commit-Position: refs/heads/master@{#296285}

DEPS

@@ -33,7 +33,7 @@ vars = {
   'pdfium_git': 'https://pdfium.googlesource.com',
   'skia_git': 'https://skia.googlesource.com',
   'boringssl_git': 'https://boringssl.googlesource.com',
-  'libvpx_revision': '42ddeba4a7ad6382898ef2e57dc4bd9f9da57aca',
+  'libvpx_revision': '55f7ba2f1239ae021542c0524b777010a1d885b6',
   'sfntly_revision': '1bdaae8fc788a5ac8936d68bf24f37d977a13dac',
   'skia_revision': 'cd523ebe2be30f268cdcec2d0b59eba609b9901b',
   # Three lines of non-changing comments so that

remoting/codec/video_encoder_vpx.cc

@@ -142,8 +142,7 @@ ScopedVpxCodec CreateVP9Codec(const webrtc::DesktopSize& size,
 
   // Use the lowest level of noise sensitivity so as to spend less time
   // on motion estimation and inter-prediction mode.
-  // Note that this is configured via the same parameter as for VP8.
-  if (vpx_codec_control(codec.get(), VP8E_SET_NOISE_SENSITIVITY, 0))
+  if (vpx_codec_control(codec.get(), VP9E_SET_NOISE_SENSITIVITY, 0))
     return ScopedVpxCodec();
 
   return codec.Pass();