switched gl_Position and gl_PointSize to sk_*

Bug: skia:
Change-Id: Ie7508991aa975c1400bac23ae49d81041a313968
Reviewed-on: https://skia-review.googlesource.com/51320
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/bench/GLVec4ScalarBench.cpp b/bench/GLVec4ScalarBench.cpp
index 7a677df..2a68381 100644
--- a/bench/GLVec4ScalarBench.cpp
+++ b/bench/GLVec4ScalarBench.cpp
@@ -119,7 +119,7 @@
     vshaderTxt.append(
             "void main()\n"
             "{\n"
-            "    gl_Position = float4(a_position, 0.0, 1.0);\n"
+            "    sk_Position = float4(a_position, 0.0, 1.0);\n"
             "    o_position = a_position;\n"
             "    o_color = a_color;\n"
             "}\n");