Rename kTexture2DISampler to kITexture2DSampler.

Also remove unused kGrSLTypeCount.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4903

Change-Id: I7f934c56515424b2668886dec2f16296a1256e2c
Reviewed-on: https://skia-review.googlesource.com/4903
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Chris Dalton <csmartdalton@google.com>
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index 0c40b60..da0eae0 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -617,7 +617,7 @@
         switch (texture->texturePriv().samplerType()) {
             case kTexture2DSampler_GrSLType:
                 return 0;
-            case kTexture2DISampler_GrSLType:
+            case kITexture2DSampler_GrSLType:
                 return 1;
             case kTexture2DRectSampler_GrSLType:
                 return 2;