Some reftests or crashtests are crashing on the android emulator in glShaderSource() when webrender is enabled. eg https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=272537824&repo=try&lineNumber=4081

glShaderSource has strings and lengths arguments. These are an array of strings which can be concatenated to create the full shader source, and the lengths of these strings. The lengths can be ommitted, in which case it should treat the strings as null-terminated. But in our case we do make use of the lengths argument, and therefore we do not null-terminate the strings. However, it appears the emulator's implementation of glShaderSource assumes that they are null-terminated: https://android.googlesource.com/device/generic/goldfish-opengl/+/refs/heads/master/system/GLESv2_enc/GL2Encoder.cpp#1759.

If we add a null terminator then we avoid the crash.

I'll file this upstream and add a workaround.

https://issuetracker.google.com/issues/143448312

The emulator's implementation of glShaderSource can crash if the source string
are not null-terminated, even though we correctly pass the lengths of the
strings. Work around this by adding a null terminator when running on the
emulator.

Depends on D51293

https://hg.mozilla.org/mozilla-central/rev/17366ca83b0c