I can take care of fixing this. It seems the GYP build is now broken (I get the same error building only content_browsertests_apk target too).

I think the only way to fix this is to flip our Android bots over to GN.

I filed  issue 610974  for that.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/tools/build.git/+/b2f7a4cd08203f20386e66e0e63d0cd926463368

commit b2f7a4cd08203f20386e66e0e63d0cd926463368
Author: kjellander@chromium.org <kjellander@chromium.org>
Date: Thu May 12 05:45:48 2016

WebRTC: Update compile targets for Android GN bots

The bots were flipped to GN in https://codereview.chromium.org/1973663002/
but the compile targets needs to be generated only from the
MB config (the android_builder_chromium_webrtc target doesn't
exist in GN).

BUG= 610959 , 610974 
TBR=phoglund@chromium.org

Review-Url: https://codereview.chromium.org/1971113002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/build@300554 0039d316-1c4b-4281-b951-d872f2087c98

[modify] https://crrev.com/b2f7a4cd08203f20386e66e0e63d0cd926463368/scripts/slave/recipe_modules/chromium_tests/chromium_webrtc.py
[modify] https://crrev.com/b2f7a4cd08203f20386e66e0e63d0cd926463368/scripts/slave/recipes/chromium.expected/full_chromium_webrtc_fyi_Android_Builder_ARM64__dbg_.json
[modify] https://crrev.com/b2f7a4cd08203f20386e66e0e63d0cd926463368/scripts/slave/recipes/chromium.expected/full_chromium_webrtc_fyi_Android_Builder__dbg_.json

The following revision refers to this bug:
  http://goto.ext.google.com/viewvc/chrome-internal?view=rev&revision=87779

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r87779 | recipe-roller@chromium.org | 2016-05-12T06:03:09.870917Z

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It's now green!