Run the download_android_tools.py in a gclient hook.

[chinmaygarde]

Originally, this was a step that had to be carried out manually. Presumably because we did not want developers to download the Android SDK and NDK if they were not targetting Android. In practice, this is rarely the case. Even the buildbots unconditionally run the script (though they don’t need Android artifacts on the Mac since there is no Mac to Android builder).

cc @jamesr @jason-simmons @abarth

[chinmaygarde]

Updated docs to remove the extra setup step.

[chinmaygarde]

A side effect of this change is that Travis now downloads Android tools for the engine job. Not sure it matters.

[jamesr]

A side effect of this change is that Travis now downloads Android tools for the engine job. Not sure it matters.

ah, maybe that's why it's not in the default set. how long does it take? does this push us close to a travis timeout?

[eseidelGoogle]

We can detect travis with environment variables and disable that if needed.

[chinmaygarde]

how long does it take? does this push us close to a travis timeout?

We don't actually build the Android engine on Travis. So it doesn't affect the results of the job in any way. Travis just has to download stuff it doesn't need. This is not new since most of what gclient does is for building the engine.

[jamesr]

There was a time when travis tried to build the engine. Maybe this is a holdover from then - @abarth would probably remember.

[abarth]

Can you rig this up so we don't download these binaries on travis? They're huge and there's no benefit to downloading them on travis:

Copying gs://mojo/android/tool/0d320c50b0ed188c7e1182388e2beb623a1d307d.tar.gz...
Downloading ...flutter/src/third_party/android_tools/sdk.tar.gz: 412.35 MiB/412.35 MiB    
Copying gs://mojo/android/tool/7b727f0d4c853c9848847839a317300cb83f4ece.tar.gz...
Downloading ...flutter/src/third_party/android_tools/ndk.tar.gz: 894.75 MiB/894.75 MiB    
Running ['python', '/home/travis/depot_tools/gsutil.py', 'cp', 'gs://mojo/android/tool/0d320c50b0ed188c7e1182388e2beb623a1d307d.tar.gz', '/home/travis/build/flutter/src/third_party/android_tools/sdk.tar.gz']
Extracting Android tools (sdk)
Running ['python', '/home/travis/depot_tools/gsutil.py', 'cp', 'gs://mojo/android/tool/7b727f0d4c853c9848847839a317300cb83f4ece.tar.gz', '/home/travis/build/flutter/src/third_party/android_tools/ndk.tar.gz']
Extracting Android tools (ndk)
Hook '/usr/bin/python src/tools/android/download_android_tools.py' took 65.51 secs

[chinmaygarde]

Can you rig this up so we don't download these binaries on travis?

I could check for a Travis specific environment variable. That would mean we need to add Travis specific logic to the hooks. Or is there a way to specify to gclient that it should skip certain named hooks?

[chinmaygarde]

Added the check in flutter/buildroot#11.

[abarth]