Mark the Virtual Memory Cage as compatible with LSAN

There is no need to wrap the cage's page allocator into a
LsanPageAllocator as that page allocator ultimately relies on the
platform page allocator to obtain pages. As the platform page allocator
will be a LsanPageAllocator when LSAN is enabled, it will already take
care of marking the pages as root regions with LSAN.

luci.v8.try:v8_linux64_heap_sandbox_dbg_ng

Bug: chromium:1218005
Change-Id: I62b5da9cb320e5012a657951c0d4c85a1bb2b3fb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3222761Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Samuel Groß <saelo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77403}

BUILD.gn

@@ -485,8 +485,7 @@ if (build_with_chromium && v8_current_cpu == "arm64" &&
 
 # Enable the virtual memory cage on 64-bit Chromium builds.
 if (build_with_chromium && v8_enable_pointer_compression_shared_cage) {
-  # The cage is incompatible with lsan.
-  v8_enable_virtual_memory_cage = !is_lsan
+  v8_enable_virtual_memory_cage = true
 }
 
 assert(!v8_disable_write_barriers || v8_enable_single_generation,
@@ -521,9 +520,6 @@ assert(
     !v8_enable_virtual_memory_cage || v8_enable_pointer_compression_shared_cage,
     "V8 VirtualMemoryCage requires the shared pointer compression cage")
 
-assert(!v8_enable_virtual_memory_cage || !is_lsan,
-       "V8 VirtualMemoryCage is currently incompatible with Leak Sanitizer")
-
 assert(
     !v8_enable_pointer_compression_shared_cage || v8_enable_pointer_compression,
     "Can't share a pointer compression cage if pointers aren't compressed")

src/utils/allocation.cc

@@ -54,7 +54,6 @@ class PageAllocatorInitializer {
       page_allocator_ = default_page_allocator.get();
     }
 #if defined(LEAK_SANITIZER)
-    static_assert(!V8_VIRTUAL_MEMORY_CAGE_BOOL, "Not currently supported");
     static base::LeakyObject<base::LsanPageAllocator> lsan_allocator(
         page_allocator_);
     page_allocator_ = lsan_allocator.get();