This change does a couple things. First, it uses the 'active attribs'
mask in the gl::Program to sort the translated attributes, instead of
checking the translated attribute themselves. This means we don't have
to consult the 'active' field of the translated attributes, which in
turns means we don't have to update the active field in the attributes,
which breaks the dependency of the attributes on the gl::Program.

Second, use a dynamically sized array for storing the cached vertex
attributes in the InputLayoutCache. This is nice because it means
we don't have to store the size of the array separately.

Also some other refactoring cleanups. Refactoring change only.

BUG=angleproject:1327

Change-Id: Iab22de92840b30674b92eca72e450673ed9f6d6d
Reviewed-on: https://chromium-review.googlesource.com/330172Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>