When inserting uniform layout info into the default uniform block, the array
sizes need to match but insertion was skipped when the uniform was a sampler.

This caused heap corruption when uniform data was written to the wrong offset
in the buffer.

BUG=angleproject:2859

Change-Id: Ia58a68870e2a4805391266dfe73fe8c8d238931d
Reviewed-on: https://chromium-review.googlesource.com/1249562
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>