Mark InstanceBase::mPlatform as still DanglingUntriaged.

The platform is destroyed before the instance, it doesn't help to set
mPlatform to nullptr as that also triggers dangling pointer detection.

Bug: dawn:2349
Change-Id: I03605fa17e49cc0dec376355298ff7731eaf4c9f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/179203
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
diff --git a/src/dawn/native/Instance.h b/src/dawn/native/Instance.h
index 9b19acf2..3c3fa6f 100644
--- a/src/dawn/native/Instance.h
+++ b/src/dawn/native/Instance.h
@@ -217,7 +217,8 @@
     wgpu::LoggingCallback mLoggingCallback = nullptr;
     raw_ptr<void> mLoggingCallbackUserdata = nullptr;
 
-    raw_ptr<dawn::platform::Platform> mPlatform = nullptr;
+    // TODO(https://crbug.com/dawn/2349): Investigate DanglingUntriaged in dawn/native.
+    raw_ptr<dawn::platform::Platform, DanglingUntriaged> mPlatform = nullptr;
     std::unique_ptr<dawn::platform::Platform> mDefaultPlatform;
 
     BackendsArray mBackends;