Roll partition_alloc + cleanup.

Roll partition_alloc and apply some cleanup. I found some targets
referring to removed files.

Diff: https://chromium.googlesource.com/chromium/src/base/allocator/partition_allocator.git/+log/f941becc7efa..2e6b2efb6f43

Bug: 351867706
Change-Id: If9c069460a442d4de66f7ebf3bb8219cda206ef9
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/197694
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/DEPS b/DEPS
index 5a92196..f9017d2 100644
--- a/DEPS
+++ b/DEPS
@@ -442,7 +442,7 @@
   # Dependencies for PartitionAlloc.
   # Doc: https://docs.google.com/document/d/1wz45t0alQthsIU9P7_rQcfQyqnrBMXzrOjSzdQo-V-A
   'third_party/partition_alloc': {
-    'url': '{chromium_git}/chromium/src/base/allocator/partition_allocator.git@f941becc7efa75971aa4e83d0cd3217f4f1ef57f',
+    'url': '{chromium_git}/chromium/src/base/allocator/partition_allocator.git@2e6b2efb6f435aa3dd400cb3bdcead2a601f8f9a',
     'condition': 'dawn_standalone',
   },
 }