Improve GLSL integer support

 - Adds shader types for uint.
 - Adds a cap for integer support.
 - Uses glVertexAttribIPointer for integer attribs.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1669853002

Committed: https://skia.googlesource.com/skia/+/3a2caf8ecf38124f4ad21a0f6c4dabfcfa17911a

Review URL: https://codereview.chromium.org/1669853002
diff --git a/include/gpu/gl/GrGLFunctions.h b/include/gpu/gl/GrGLFunctions.h
index 118269b..4d0d654 100644
--- a/include/gpu/gl/GrGLFunctions.h
+++ b/include/gpu/gl/GrGLFunctions.h
@@ -178,6 +178,7 @@
 typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLVertexAttrib3fvProc)(GrGLuint indx, const GrGLfloat* values);
 typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLVertexAttrib4fvProc)(GrGLuint indx, const GrGLfloat* values);
 typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLVertexAttribDivisorProc)(GrGLuint index, GrGLuint divisor);
+typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLVertexAttribIPointerProc)(GrGLuint indx, GrGLint size, GrGLenum type, GrGLsizei stride, const GrGLvoid* ptr);
 typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLVertexAttribPointerProc)(GrGLuint indx, GrGLint size, GrGLenum type, GrGLboolean normalized, GrGLsizei stride, const GrGLvoid* ptr);
 typedef GrGLvoid (GR_GL_FUNCTION_TYPE* GrGLViewportProc)(GrGLint x, GrGLint y, GrGLsizei width, GrGLsizei height);