Rename variables named `input` in test files.

`input` is a reserved word in GLSL. http://screen/85m4iRwvJRadKbV

Change-Id: Iffc0a47d916a2419a27767902c839e09bfa7fe26
Bug: skia:11115
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/454736
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
diff --git a/resources/sksl/intrinsics/Atanh.sksl b/resources/sksl/intrinsics/Atanh.sksl
index c8a01ce..2d5c121 100644
--- a/resources/sksl/intrinsics/Atanh.sksl
+++ b/resources/sksl/intrinsics/Atanh.sksl
@@ -1,12 +1,12 @@
-uniform half4 input, expected;
+uniform half4 inputVal, expected;
 uniform half4 colorGreen, colorRed;
 
 half4 main(float2 coords) {
     const half4 constVal1 = half4(0, 0.2449186624037091292, 0.46211715726000975, 0.761594155955764);
-    return (atanh(input.x)        == expected.x     &&
-            atanh(input.xy)       == expected.xy    &&
-            atanh(input.xyz)      == expected.xyz   &&
-            atanh(input.xyzw)     == expected.xyzw  &&
+    return (atanh(inputVal.x)     == expected.x     &&
+            atanh(inputVal.xy)    == expected.xy    &&
+            atanh(inputVal.xyz)   == expected.xyz   &&
+            atanh(inputVal.xyzw)  == expected.xyzw  &&
             atanh(constVal1.x)    == expected.x     &&
             atanh(constVal1.xy)   == expected.xy    &&
             atanh(constVal1.xyz)  == expected.xyz   &&