GLES2: uniform struct{sampler} as a function arg

GLES2: uniform struct{sampler} as a function arg

(Some of?) these tests failed on Pixel2016/7.0 (they were
fixed in 8.0 and pass on Pixel2016/8.1):
  https://crbug.com/695680
This is a port from WebGL:
  https://github.com/KhronosGroup/WebGL/blob/master/sdk/tests/conformance/glsl/bugs/sampler-struct-function-arg.html

New tests:
  dEQP-GLES2.functional.shaders.struct.uniform.sampler_in_function_arg_vertex
  dEQP-GLES2.functional.shaders.struct.uniform.sampler_in_function_arg_fragment
  dEQP-GLES2.functional.shaders.struct.uniform.sampler_in_array_function_arg_vertex
  dEQP-GLES2.functional.shaders.struct.uniform.sampler_in_array_function_arg_fragment
Components: AOSP

Change-Id: Ic71a7969c9bcf481c12b95a99e6379cfec659a8e