Add more robust shader API for querying variable properties

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Currently we use ShGetActiveUniform to return a description of a shared 
global/uniform. This method currently is limited:

 * by not returning the ordering of the variables, structures cannot be properly validated
 * determining the correct validation error from a list of field names, not grouped by structure, takes some reverse engineering effort. 
 * In ES3, we also need the interpolation mode associated with the variable (flat/centroid/etc), which is necessary for link validation.
 * It may also be useful to pass back an array size, with zero for scalar values, instead of parsing this information from a name.
 * possibly other complications with structures?

It might be a good approach to return a block of memory which is organized more 
akin to a tree, where structs are organized as a typed list of fields.

Original issue reported on code.google.com by jmad...@chromium.org on 21 Aug 2013 at 4:01

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Original comment by jmad...@chromium.org on 10 Oct 2013 at 9:31

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Original comment by c...@chromium.org on 7 Dec 2013 at 4:00

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FYI: I am adding test cases to make sure the struct type matching behaviors are 
correct

https://github.com/KhronosGroup/WebGL/pull/481

Original comment by zmo@chromium.org on 27 Feb 2014 at 7:07

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Awesome, thanks!

Original comment by jmad...@chromium.org on 27 Feb 2014 at 8:00

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Original comment by jmad...@chromium.org on 13 May 2014 at 6:32

• Changed state: Started

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API is complete as of https://chromium-review.googlesource.com/#/c/213501/. 
invariant support (issue 711) not yet finished, with everything else being more 
or less complete.

Original comment by jmad...@chromium.org on 3 Sep 2014 at 8:37

• Changed state: Fixed