I'm not sure why yet, but when using angle in skia,
getIntegerv(GL_MAX_VERTEX_ATTRIBS, &maxVertexAttribs) sometimes fails,
and when that happens we attempt to allocate and array with the size of
maxVertexAttribs, which is uninitialized, which could be huge.

Prevent this by initializing the variable.

Also sweep through other similar calls and ensure that these use
initialized values (test code has not been updated)

BUG=skia:4380

Change-Id: If1f3cf72f2b2829ad3933637af8778d574a20f61
Reviewed-on: https://chromium-review.googlesource.com/307239Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tryjob-Request: Jamie Madill <jmadill@chromium.org>
Tryjob-Request: Dian Xiang <dianx@google.com>
Tested-by: Hendrik Wagenaar <hendrikw@chromium.org>