Remove incorrect length check

The DCHECK in the lookup method compares the stashed length of the backing store
and the byte_length queried on lookup. These two are not guaranteed to be equal
as there can be grow calls that update the lenght of the buffer between the
length being stashed and the equality check.

Bug: chromium:1010272
Change-Id: I754fa0a9ab676cd838e893d12ef6b13fc7d335e1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1911490Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Deepti Gandluri <gdeepti@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65003}

src/objects/backing-store.cc

@@ -629,8 +629,14 @@ std::shared_ptr<BackingStore> GlobalBackingStoreRegistry::Lookup(
     return std::shared_ptr<BackingStore>();
   }
   auto backing_store = result->second.lock();
-  DCHECK_EQ(buffer_start, backing_store->buffer_start());
-  DCHECK_EQ(length, backing_store->byte_length());
+  CHECK_EQ(buffer_start, backing_store->buffer_start());
+  if (backing_store->is_wasm_memory()) {
+    // Grow calls to shared WebAssembly threads can be triggered from different
+    // workers, length equality cannot be guaranteed here.
+    CHECK_LE(length, backing_store->byte_length());
+  } else {
+    CHECK_EQ(length, backing_store->byte_length());
+  }
   return backing_store;
 }