ES31: Add Geometry Shader layout qualifiers in GLSL compiler This patch intends to implement Geometry Shader layout qualifiers required in OpenGL ES 3.1 extension GL_OES_geometry_shader in ANGLE GLSL compiler. 1. Add support to the shader type GL_GEOMETRY_SHADER_OES. 2. Implement Geometry Shader layout qualifiers in the GLSL compiler: (1) Add support to OpenGL ES 3.1 extension "GL_OES_geometry_shader". (2) Add validations of the input and output primitive declarations in the Geometry Shader layout declarations. (3) Add 'invocations' and 'max_vertices' support in the Geometry Shader layout declarations 3. Add unit tests to cover all the new features added in this patch. BUG=angleproject:1941 TEST=angle_unittests Change-Id: Ie693e11f8a00dab3552626ed63e9336c7fbd3cb8 Reviewed-on: https://chromium-review.googlesource.com/560647 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org>