Exclude BigEndianWriter::end_ from rewrite_raw_ptr_fields

This field points past the end of an allocation; therefore, it can
refer to an invalid allocation slot, which will lead to a crash in
the CheckedPtr constructor.

Bug: 1158039
Change-Id: Iaa141a51e680994a4c6bc9aabb6039621424706b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2611704
Auto-Submit: Sergei Glazunov <glazunov@google.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840290}

tools/clang/rewrite_raw_ptr_fields/manual-fields-to-ignore.txt

@@ -128,6 +128,10 @@ views::internal::ClassPropertyValueSetter::property_  # passed to templated para
 (anonymous namespace)::ScopedFunctionHelper::function_  # function pointer template
 KeyedServiceBaseFactory::service_name_ # used in decltype
 
+# Populated manually - this field points past the end of an allocation;
+# therefore, it can refer to an invalid allocation slot
+base::BigEndianWriter::end_
+
 #######
 # CheckedPtr2/MTECheckedPtr-specific sections
 #######