Improve GLSL integer support

src/gpu/gl/GrGLInterface.cpp

Index: src/gpu/gl/GrGLInterface.cpp
diff --git a/src/gpu/gl/GrGLInterface.cpp b/src/gpu/gl/GrGLInterface.cpp
index 925f081b342bb733001829bc9edb51719292de5b..c09efae2b88bd87007efdcfdda0209fd368d44f2 100644
--- a/src/gpu/gl/GrGLInterface.cpp
+++ b/src/gpu/gl/GrGLInterface.cpp
@@ -416,6 +416,13 @@ bool GrGLInterface::validate() const {
         }
     }
 
+    // glVertexAttribIPointer was added in version 3.0 of both desktop and ES.
+    if (glVer >= GR_GL_VER(3, 0)) {
+        if (NULL == fFunctions.fVertexAttribIPointer) {
+            RETURN_FALSE_INTERFACE
+        }
+    }
+
     if (kGL_GrGLStandard == fStandard) {
         if (glVer >= GR_GL_VER(3, 0) || fExtensions.has("GL_ARB_vertex_array_object")) {
             if (nullptr == fFunctions.fBindVertexArray ||