Default pdfium to using an optimized allocator.

Improve debug build performance since we are not debugging the
allocator itself.

Change-Id: I0144a24f6048fa79ad5a0891fd3e9056edcec032
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/128330
Reviewed-by: Thomas Sepez <tsepez@google.com>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
diff --git a/.gn b/.gn
index 6a6bbb0..02a548a 100644
--- a/.gn
+++ b/.gn
@@ -9,6 +9,12 @@
 script_executable = "python3"
 
 default_args = {
+  # Use a production-performant allocator.
+  # TODO(tsepez): `enable_pkeys` is a workaround for a partition-alloc build
+  # issue and should be removed.
+  partition_alloc_is_debug = false
+  enable_pkeys = false
+
   # PDFs only need to run JavaScript.
   v8_enable_webassembly = false