Revert "Remove support for Valgrind in ART."

This reverts commit 8268cb677bd92bfbcfec7e803775c29687494e53.

Reason for revert: ASAN failures

Change-Id: I7e66d3f3fb461ae4f6dea6ec7d506b7dface3402
Test: SANITIZE_HOST=address m test-art-host
Bug: 77856586
Bug: 29282211
diff --git a/runtime/gc/allocator/rosalloc.h b/runtime/gc/allocator/rosalloc.h
index 30213d5..150fe95 100644
--- a/runtime/gc/allocator/rosalloc.h
+++ b/runtime/gc/allocator/rosalloc.h
@@ -625,7 +625,7 @@
 
   // If true, check that the returned memory is actually zero.
   static constexpr bool kCheckZeroMemory = kIsDebugBuild;
-  // Do not check memory when running under a memory tool. In a normal
+  // Valgrind protects memory, so do not check memory when running under valgrind. In a normal
   // build with kCheckZeroMemory the whole test should be optimized away.
   // TODO: Unprotect before checks.
   ALWAYS_INLINE bool ShouldCheckZeroMemory();
@@ -768,7 +768,7 @@
   // greater than or equal to this value, release pages.
   const size_t page_release_size_threshold_;
 
-  // Whether this allocator is running on a memory tool.
+  // Whether this allocator is running under Valgrind.
   bool is_running_on_memory_tool_;
 
   // The base address of the memory region that's managed by this allocator.