To use the Chromium toolchain out-of-the-box,
it seems like an All target is needed by default.

To compile using the Android tools:
1. add ;target_os=['android'] to your .gclient
2. gclient sync --nohooks
3. from your trunk dir, run:
   source build/android/envsetup.sh
4. gclient runhooks
5. ninja -C out/Release

BUG=libyuv:288
R=wuwang@google.com

Review URL: https://webrtc-codereview.appspot.com/4119007

git-svn-id: http://libyuv.googlecode.com/svn/trunk@873 16f28f9a-4ce2-e073-06de-1de4eb20be90