Switch to C++20 by default

Bug: pdfium:1932
Change-Id: I1afabb0049f48756cb3aeb723f7f6fbeb719486c
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/112170
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

pdfium.gni

diff --git a/pdfium.gni b/pdfium.gni
index ffa740a..6692dd7 100644
--- a/pdfium.gni
+++ b/pdfium.gni
@@ -39,7 +39,7 @@
   # Build PDFium using C++20 if set to true. Otherwise builds with C++17.
   # There is no "pdf_use_cxx20_override" variable because this is only used in
   # standalone PDFium, and not when PDFium is embedded in our projects.
-  pdf_use_cxx20 = (is_win && is_component_build) || is_fuchsia
+  pdf_use_cxx20 = true
 
   # Build PDFium against PartitionAlloc. When false, PDFium must build without
   # requiring any PartitionAlloc headers or code to be present. When true,