Update references to Mac OS X in comments.

OS X -> macOS.

Change-Id: I8a3f4a66b39272f62801ae1d36730ca4e0ef0741
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/72233
Reviewed-by: Daniel Hosseinian <dhoss@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/build_overrides/gtest.gni b/build_overrides/gtest.gni
index bf30fb1..d788258 100644
--- a/build_overrides/gtest.gni
+++ b/build_overrides/gtest.gni
@@ -8,7 +8,7 @@
 # Exclude support for platform-specific operations across unit tests.
 gtest_include_platform_test = false
 
-# Exclude support for testing Objective C code on OS X and iOS.
+# Exclude support for testing Objective C code on macOS and iOS.
 gtest_include_objc_support = false
 
 # Exclude support for flushing coverage files on iOS.
diff --git a/samples/pdfium_test.cc b/samples/pdfium_test.cc
index 9ad851f..fb92deb 100644
--- a/samples/pdfium_test.cc
+++ b/samples/pdfium_test.cc
@@ -66,7 +66,7 @@
 #define R_OK 4
 #endif
 
-// wordexp is a POSIX function that is only available on OSX and non-Android
+// wordexp is a POSIX function that is only available on macOS and non-Android
 // Linux platforms.
 #if defined(__APPLE__) || (defined(__linux__) && !defined(__ANDROID__))
 #define WORDEXP_AVAILABLE