When V8_ENABLE_SANDBOX is enabled, all ArrayBuffer backing stores must be allocated within the V8 memory cage — external pointers cannot be directly wrapped and must be copied into V8-managed memory instead. This commit refactors allocators in node_buffer.cc, node_serdes.cc, and node_trace_events.cc to route allocations through ArrayBuffer::Allocator::NewDefaultAllocator() when the sandbox is enabled, ensuring memory lands inside the cage. In node_serdes.cc, ValueSerializer::Delegate is also extended with ReallocateBufferMemory/FreeBufferMemory overrides so the serializer's internal buffer is cage-allocated from the start.

Tested by making the following change:

diff --git a/configure.py b/configure.py
index fa47e9c4854..f4342d2c718 100755
--- a/configure.py
+++ b/configure.py
@@ -2047,7 +2047,7 @@ def configure_v8(o, configs):
   # Until we manage to get rid of all those, v8_enable_sandbox cannot be used.
   # Note that enabling pointer compression without enabling sandbox is unsupported by V8,
   # so this can be broken at any time.
-  o['variables']['v8_enable_sandbox'] = 0
+  o['variables']['v8_enable_sandbox'] = 1 if options.enable_pointer_compression else 0
   # We set v8_enable_pointer_compression_shared_cage to 0 always, even when
   # pointer compression is enabled so that we don't accidentally enable shared
   # cage mode when pointer compression is on.

and running with ./configure --ninja --experimental-enable-pointer-compression

This allows Electron to reduce/remove a patch.