Convert to absl::optional, part 1.

Search and replace. Then clang-format. Leave the headers alone for now.

Bug: pdfium:1726
Change-Id: I14612c871e16dd2fc0c69555171a55b71fa937cd
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/85517
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/fxjs/cjs_util.cpp b/fxjs/cjs_util.cpp
index 8a346d1..0a27b57 100644
--- a/fxjs/cjs_util.cpp
+++ b/fxjs/cjs_util.cpp
@@ -112,7 +112,8 @@
   {
     size_t offset = 0;
     while (true) {
-      Optional<size_t> offset_end = unsafe_fmt_string.Find(L"%", offset + 1);
+      absl::optional<size_t> offset_end =
+          unsafe_fmt_string.Find(L"%", offset + 1);
       if (!offset_end.has_value()) {
         unsafe_conversion_specifiers.push_back(
             unsafe_fmt_string.Last(unsafe_fmt_string.GetLength() - offset));