[Freestyler] Max timeout of Observation

Race the Observation with a timeout Promise and report the correct
error to the LLM so that it can try to recover.
This mitigates the issue of SideEffect's and Observations getting
stuck due to Promises that never resolve.

Fixed: 373893673
Change-Id: I209c3b07244bd8412fce5e4c0e47e4af1fbf6f77
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/5993651
Commit-Queue: Nikolay Vitkov <[email protected]>
Auto-Submit: Nikolay Vitkov <[email protected]>
Reviewed-by: Alex Rudenko <[email protected]>

Author: Lightning00Blade

front_end/panels/freestyler/FreestylerAgent.ts

@@ -194,6 +194,7 @@ async function executeJsCode(
 }
 
 const MAX_OBSERVATION_BYTE_LENGTH = 25_000;
+const OBSERVATION_TIMEOUT = 5_000;
 
 type CreateExtensionScopeFunction = (changes: ChangeManager) => {
   install(): Promise<void>, uninstall(): Promise<void>,
@@ -453,10 +454,16 @@ export class FreestylerAgent extends AiAgent<SDK.DOMModel.DOMNode> {
           canceled: true,
         };
       }
-      const result = await this.#execJs(
-          functionDeclaration,
-          {throwOnSideEffect},
-      );
+      const result = await Promise.race([
+        this.#execJs(
+            functionDeclaration,
+            {throwOnSideEffect},
+            ),
+        new Promise<never>((_, reject) => {
+          setTimeout(
+              () => reject(new Error('Script execution exceeded the maximum allowed time.')), OBSERVATION_TIMEOUT);
+        }),
+      ]);
       const byteCount = Platform.StringUtilities.countWtf8Bytes(result);
       Host.userMetrics.freestylerEvalResponseSize(byteCount);
       if (byteCount > MAX_OBSERVATION_BYTE_LENGTH) {