Make sure WebRTC works without libvpx VP9 support.

Wires up existing libvpx_build_vp9==0 GYP flag into WebRTC and makes VP9
optional. Change is GYP only for now since libvpx's GN files build VP9
unconditionally.

BUG=webrtc:5884
R=kjellander@webrtc.org

Review URL: https://codereview.webrtc.org/1970343002 .

Cr-Commit-Position: refs/heads/master@{#12741}

webrtc/modules/video_coding/codecs/test/videoprocessor_integrationtest.cc

@@ -626,6 +626,7 @@ TEST_F(VideoProcessorIntegrationTest, Process0PercentPacketLossH264) {
 // Fails on iOS. See webrtc:4755.
 #if !defined(WEBRTC_IOS)
 
+#if !defined(RTC_DISABLE_VP9)
 // VP9: Run with no packet loss and fixed bitrate. Quality should be very high.
 // One key frame (first frame only) in sequence. Setting |key_frame_interval|
 // to -1 below means no periodic key frames in test.
@@ -780,6 +781,8 @@ TEST_F(VideoProcessorIntegrationTest, ProcessNoLossSpatialResizeFrameDropVP9) {
 // TODO(marpan): Add temporal layer test for VP9, once changes are in
 // vp9 wrapper for this.
 
+#endif  // !defined(RTC_DISABLE_VP9)
+
 // VP8: Run with no packet loss and fixed bitrate. Quality should be very high.
 // One key frame (first frame only) in sequence. Setting |key_frame_interval|
 // to -1 below means no periodic key frames in test.

webrtc/modules/video_coding/codecs/vp9/include/vp9.h

@@ -18,6 +18,7 @@ namespace webrtc {
 
 class VP9Encoder : public VideoEncoder {
  public:
+  static bool IsSupported();
   static VP9Encoder* Create();
 
   virtual ~VP9Encoder() {}
@@ -25,6 +26,7 @@ class VP9Encoder : public VideoEncoder {
 
 class VP9Decoder : public VideoDecoder {
  public:
+  static bool IsSupported();
   static VP9Decoder* Create();
 
   virtual ~VP9Decoder() {}

webrtc/modules/video_coding/codecs/vp9/vp9.gyp

@@ -20,6 +20,21 @@
             '<(libvpx_dir)/libvpx.gyp:libvpx',
           ],
         }],
+        ['libvpx_build_vp9==1', {
+          'sources': [
+            'screenshare_layers.cc',
+            'screenshare_layers.h',
+            'vp9_frame_buffer_pool.cc',
+            'vp9_frame_buffer_pool.h',
+            'vp9_impl.cc',
+            'vp9_impl.h',
+          ],
+        }, {
+          'sources': [
+            'vp9_noop.cc',
+          ],
+        }
+        ],
       ],
       'dependencies': [
         '<(webrtc_root)/common_video/common_video.gyp:common_video',
@@ -28,12 +43,6 @@
       ],
       'sources': [
         'include/vp9.h',
-        'screenshare_layers.cc',
-        'screenshare_layers.h',
-        'vp9_frame_buffer_pool.cc',
-        'vp9_frame_buffer_pool.h',
-        'vp9_impl.cc',
-        'vp9_impl.h',
       ],
     },
   ],

webrtc/modules/video_coding/codecs/vp9/vp9_impl.cc

@@ -47,6 +47,10 @@ int GetCpuSpeed(int width, int height) {
 #endif
 }
 
+bool VP9Encoder::IsSupported() {
+  return true;
+}
+
 VP9Encoder* VP9Encoder::Create() {
   return new VP9EncoderImpl();
 }
@@ -823,6 +827,10 @@ const char* VP9EncoderImpl::ImplementationName() const {
   return "libvpx";
 }
 
+bool VP9Decoder::IsSupported() {
+  return true;
+}
+
 VP9Decoder* VP9Decoder::Create() {
   return new VP9DecoderImpl();
 }

webrtc/modules/video_coding/codecs/vp9/vp9_noop.cc

@@ -0,0 +1,39 @@
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ *
+ */
+
+#if !defined(RTC_DISABLE_VP9)
+#error
+#endif  // !defined(RTC_DISABLE_VP9)
+
+#include "webrtc/base/checks.h"
+#include "webrtc/modules/video_coding/codecs/vp9/include/vp9.h"
+
+namespace webrtc {
+
+bool VP9Encoder::IsSupported() {
+  return false;
+}
+
+VP9Encoder* VP9Encoder::Create() {
+  RTC_NOTREACHED();
+  return nullptr;
+}
+
+bool VP9Decoder::IsSupported() {
+  return false;
+}
+
+VP9Decoder* VP9Decoder::Create() {
+  RTC_NOTREACHED();
+  return nullptr;
+}
+
+}  // namespace webrtc