Treat browser ui target type as frame target in the frontend.

We are adding a new browser_ui frame target type for browser ui in a
webui browser. This change ensures that the new target type is treated
as frame target in frondend.
The related chromium.src change is at http://crrev.com/c/6990317.

Bug: 393144165
Change-Id: If2b3b8ae0f17bee089fa9feb8c16e4e7d4204730
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/7018087
Reviewed-by: Danil Somsikov <dsv@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Liang Zhao <lzhao@microsoft.com>

Author: LiangTheDev

front_end/core/sdk/ChildTargetManager.test.ts

@@ -55,6 +55,7 @@ describeWithMockConnection('ChildTargetManager', () => {
              ['background_page', SDK.Target.Type.FRAME],
              ['app', SDK.Target.Type.FRAME],
              ['popup_page', SDK.Target.Type.FRAME],
+             ['browser_ui', SDK.Target.Type.FRAME],
              ['worker', SDK.Target.Type.Worker],
              ['shared_worker', SDK.Target.Type.SHARED_WORKER],
              ['service_worker', SDK.Target.Type.ServiceWorker],

front_end/core/sdk/ChildTargetManager.ts

@@ -177,6 +177,8 @@ export class ChildTargetManager extends SDKModel<EventTypes> implements Protocol
       type = Type.FRAME;
     } else if (targetInfo.type === 'page') {
       type = Type.FRAME;
+    } else if (targetInfo.type === 'browser_ui') {
+      type = Type.FRAME;
     } else if (targetInfo.type === 'worker') {
       type = Type.Worker;
     } else if (targetInfo.type === 'worklet') {