[a11y] Remove spurious trace event for BlinkAXTreeSource::SerializeNode

Looks like through bitrot this is tracing ~nothing?
At the same time the overhead adds up. For instrumented builds with tracing, it's taking ~1/3 of samples for BlinkAXTreeSource::SerializeNode

Change-Id: I56d20c366dee9daa0801f789006b9e00e1f61d94
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3899638
Reviewed-by: Daniel Libby <dlibby@microsoft.com>
Commit-Queue: Yaron Friedman <yfriedman@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1048098}

third_party/blink/renderer/modules/accessibility/blink_ax_tree_source.cc

@@ -19,7 +19,6 @@
 #include "third_party/blink/renderer/modules/accessibility/ax_object_cache_impl.h"
 #include "third_party/blink/renderer/modules/accessibility/ax_selection.h"
 #include "third_party/blink/renderer/platform/heap/collection_support/heap_deque.h"
-#include "third_party/blink/renderer/platform/instrumentation/tracing/trace_event.h"
 #include "ui/accessibility/accessibility_features.h"
 #include "ui/accessibility/accessibility_switches.h"
 #include "ui/accessibility/ax_common.h"
@@ -399,9 +398,6 @@ void BlinkAXTreeSource::SerializeNode(AXObject* src,
     dst->AddStringAttribute(ax::mojom::blink::StringAttribute::kImageDataUrl,
                             src->ImageDataUrl(max_image_data_size_).Utf8());
   }
-
-  TRACE_EVENT2("accessibility", "BlinkAXTreeSource::SerializeNode", "role",
-               ui::ToString(dst->role), "id", dst->id);
 }
 
 void BlinkAXTreeSource::Trace(Visitor* visitor) const {