[inspector-test] Gracefully handle termination.

Reporting messages can trigger termination in case of `inspector-test`,
which we need to be able to deal with gracefully for the fuzzer.

Fixed: chromium:1307449
Change-Id: I88ba2b13d920134a1670b808adc4ace4ca6d1dff
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3540260
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79543}

test/inspector/isolate-data.cc

@@ -339,10 +339,16 @@ void InspectorIsolateData::PromiseRejectHandler(v8::PromiseRejectMessage data) {
   int exception_id = HandleMessage(
       v8::Exception::CreateMessage(isolate, exception), exception);
   if (exception_id) {
-    promise
-        ->SetPrivate(isolate->GetCurrentContext(), id_private,
-                     v8::Int32::New(isolate, exception_id))
-        .ToChecked();
+    if (promise
+            ->SetPrivate(isolate->GetCurrentContext(), id_private,
+                         v8::Int32::New(isolate, exception_id))
+            .IsNothing()) {
+      // Handling the |message| above calls back into JavaScript (by reporting
+      // it via CDP) in case of `inspector-test`, and can lead to terminating
+      // execution on the |isolate|, in which case the API call above will
+      // return immediately.
+      DCHECK(isolate->IsExecutionTerminating());
+    }
   }
 }