egltrace/android: Write to /sdcard rather than /data

[nigels-com]

Ordinarily apitrace on Android requires a rooted device.
Change the output destination from /data to /sdcard so that
applications with apitrace built-in with WRITE_EXTERNAL_STORAGE
permission can write traces on non-rooted devices too.

[jrfonseca]

Sounds good but I don't use Android. Assuming the others who do (e.g. @amonakov) have no objection, please update the instructions Dalvik.markdown too.

PS: Probably it would be better to send Android related review requests to the mailing list, as I really don't know enough to make an opinion.

[nigels-com]

Sure, will do.

[amonakov]

NAK. This is going to break tracing applications without sdcard write permission when /sdcard is a fat32 partition, or resides on a fuse filesystem not supporting chmod 0777.

A better approach would be to place trace files into /data/data/$procname. I'll try to submit patches for that soon.

[nigels-com]

Perhaps then an optional overide that can be set via an environment variable or directly by the linked application?
Using apitrace as a library (rather than invisible interposer) suggests that the application ought to decide where the output ought to go.

• Nigel

[amonakov]

Well, an environment variable already exists: TRACE_FILE.

[nigels-com]

Closing this in favor of pull request 150.
#150
Thanks all!