[Backport] CVE-2021-30562: Use after free in WebSerial

Cherry-pick of patch originally reviewed on
https://chromium-review.googlesource.com/c/chromium/src/+/3041456:
serial: Fix parent class tracing for SerialPort

When SerialPort was updated to be ActiveScriptWrappable and an
EventTarget the Trace method was not updated to call the parent class
trace methods.

(cherry picked from commit 4059ecc3a5352601a4d79196f90c8ca19262afe1)

Bug: 1220078
Change-Id: If6967a913268bce86d4488359a9418a814530f84
Auto-Submit: Reilly Grant <[email protected]>
Commit-Queue: Tom Sepez <[email protected]>
Reviewed-by: Tom Sepez <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#893039}
Reviewed-by: Jana Grill <[email protected]>
Owners-Override: Jana Grill <[email protected]>
Commit-Queue: Roger Felipe Zanoni da Silva <[email protected]>
Cr-Commit-Position: refs/branch-heads/4430@{#1541}
Cr-Branched-From: e5ce7dc4f7518237b3d9bb93cccca35d25216cbe-refs/heads/master@{#857950}
Reviewed-by: Allan Sandfeld Jensen <[email protected]>

Author: reillyeon

chromium/third_party/blink/renderer/modules/serial/serial_port.cc

@@ -508,7 +508,8 @@ void SerialPort::Trace(Visitor* visitor) const {
   visitor->Trace(open_resolver_);
   visitor->Trace(signal_resolvers_);
   visitor->Trace(close_resolver_);
-  ScriptWrappable::Trace(visitor);
+  EventTargetWithInlineData::Trace(visitor);
+  ActiveScriptWrappable<SerialPort>::Trace(visitor);
 }
 
 bool SerialPort::HasPendingActivity() const {