Disable libyuv jpeg support on Android

webrtc/supplement.gypi

 {
   'variables': {
     'variables': {
       'webrtc_root%': '<(DEPTH)/webrtc',
       # Override the defaults in Chromium's build/common.gypi.
       # Needed for ARC and libc++.
       'mac_sdk_min%': '10.11',
       'mac_deployment_target%': '10.7',
     },
     'webrtc_root%': '<(webrtc_root)',
     'mac_deployment_target%': '<(mac_deployment_target)',
     'use_sysroot%': '<(use_sysroot)',
     'build_with_chromium': 0,
     'conditions': [
       ['OS=="ios"', {
         # Set target_subarch for if not already set. This is needed because the
         # Chromium iOS toolchain relies on target_subarch being set.
         'conditions': [
           ['target_arch=="arm" or target_arch=="ia32"', {
             'target_subarch%': 'arm32',
           }],
           ['target_arch=="arm64" or target_arch=="x64"', {
             'target_subarch%': 'arm64',
           }],
         ],
       }],
+      ['OS=="android"', {
+        # MJPEG capture is not used on Android. Disable to reduce
+        # libjingle_peerconnection_so file size.
+        'libyuv_disable_jpeg%': 1,

[kjellander_webrtc, 2016/05/16 14:23:22]

You only need to put a variable in supplement.gypi if you're going to override a
default value in Chromium's build/common.gypi.

For this case, store it in webrtc/build/common.gypi instead, since it's only
read in https://chromium.googlesource.com/libyuv/libyuv/+/master/libyuv.gyp#21

That said, it looks like we need to introduce the variable in GN as well, but
it's not important to do now since the builds we're targeting with this
optimization are based on GYP.

[magjed_webrtc, 2016/05/17 08:45:56]

I tried moving it to webrtc/build/common.gypi, but then libjpeg_turbo got
included in libjingle_peerconnection_so again, so it doesn't work. I don't know
how the include order works for these files, but I guess libyuv.gyp is included
before webrtc/build/common.gypi.

[kjellander_webrtc, 2016/05/17 14:07:49]

Oh dear, GYP trickery. We chatted offline and came to the conclusion that this
must be because libyuv.gyp doesn't include our webrtc/build/common.gypi, so it
probably gets its own environment of GYP variables. If that's how it works, we
need to set this in the global GYP scope, which means this actually is the right
place!

+      }],
     ],
   },
   'target_defaults': {
     'target_conditions': [
       ['_target_name=="sanitizer_options"', {
         'conditions': [
           ['lsan==1', {
             # Replace Chromium's LSan suppressions with our own for WebRTC.
             'sources/': [
               ['exclude', 'lsan_suppressions.cc'],
             ],
             'sources': [
               '<(webrtc_root)/build/sanitizers/lsan_suppressions_webrtc.cc',
             ],
           }],
           ['tsan==1', {
             # Replace Chromium's TSan v2 suppressions with our own for WebRTC.
             'sources/': [
               ['exclude', 'tsan_suppressions.cc'],
             ],
             'sources': [
               '<(webrtc_root)/build/sanitizers/tsan_suppressions_webrtc.cc',
             ],
           }],
         ],
       }],
     ],
   },
 }