1. The current implementation misused the offset in gBinaryData as the
memcpy size. This CL fixed it by adding the byte size into the
UpdateClientArrayPointer call.
2. Trying passing a pointer to a C-style array parameter which causes
compiling error. This CL fixed by simply use const void * to do memcpy.
3. Able to run frame capture successfully for the first 100 frames of
glmark2.

Bug: angleproject:3611
Change-Id: Ibaef224c2a2d124b681757d9ecd187a5f9b7079b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1721207
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>