Replaced all calls to fragmentPosition() with sk_FragCoord

Change-Id: I2ed4558aea74b3ae7ee11dfe4736cdbcb16ae49e
Reviewed-on: https://skia-review.googlesource.com/8278
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/tests/SkSLErrorTest.cpp b/tests/SkSLErrorTest.cpp
index 9c34ab4..301281c 100644
--- a/tests/SkSLErrorTest.cpp
+++ b/tests/SkSLErrorTest.cpp
@@ -421,4 +421,13 @@
                  "error: 1: division by zero\n1 error\n");
 }
 
+DEF_TEST(SkSLUnsupportedGLSLIdentifiers, r) {
+    test_failure(r,
+                 "void main() { float x = gl_FragCoord.x; };",
+                 "error: 1: unknown identifier 'gl_FragCoord'\n1 error\n");
+    test_failure(r,
+                 "void main() { float r = gl_FragColor.r; };",
+                 "error: 1: unknown identifier 'gl_FragColor'\n1 error\n");
+}
+
 #endif