feat(content): add includeShadow option to page.content()

[Yury Semikhatsky (yury-s)]

Summary

• Adds includeShadow option to page.content() and frame.content().
• When set, open shadow roots are serialized as declarative shadow DOM (<template shadowrootmode="open">) via Element.getHTML(). Closed roots are not accessible from script and are not included.
• Previously requested in [Feature]: Support ShadowDOM for Page.content() #30816 and [Question] How to get shadow DOM content? #16722.

Fixes #42794

[github-actions]

Test results for "tests 1"

7 flaky

⚠️ [chromium-library] › library/video.spec.ts:725 › screencast › should capture full viewport on hidpi `@chromium-ubuntu-22.04-arm-node20`
⚠️ [chromium-library] › library/chromium/chromium.spec.ts:301 › should report intercepted service worker requests in HAR `@realtime-time-library-chromium-linux`
⚠️ [chromium-library] › library/video.spec.ts:690 › screencast › should capture full viewport `@realtime-time-library-chromium-linux`
⚠️ [chromium-library] › library/popup.spec.ts:260 › should not throw when click closes popup `@chromium-ubuntu-22.04-node22`
⚠️ [chromium-library] › library/video.spec.ts:690 › screencast › should capture full viewport `@chromium-ubuntu-22.04-node22`
⚠️ [firefox-library] › library/browsercontext-cookies-third-party.spec.ts:257 › third party 'Partitioned;' cookies `@firefox-ubuntu-22.04-node20`
⚠️ [firefox-library] › library/browsercontext-cookies-third-party.spec.ts:470 › top level 'Partitioned;' cookie and same origin iframe `@firefox-ubuntu-22.04-node20`

50478 passed, 1242 skipped

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Merge workflow run.

[github-actions]

Test results for "MCP"

1 failed
❌ [firefox] › mcp/cli-session.spec.ts:54 › idle timeout shuts the session down @mcp-windows-latest-firefox

8691 passed, 1474 skipped

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Merge workflow run.

[github-actions]

Hi, I'm the Playwright bot and I triaged the failing CI run here.

🟢 The one failure is a known pre-existing flake — this PR is clear

[firefox] › mcp/cli-session.spec.ts:54 › idle timeout shuts the session down fails only on the mcp-windows-latest-firefox bot, and it does so on main pushes too — 48 of 148 runs red (32%), on SHAs this PR can't be responsible for.

Details

Pre-existing flake / infra

• [firefox] › mcp/cli-session.spec.ts:54 › idle timeout shuts the session down (@mcp-windows-latest-firefox) — bimodal across the aggregated CI results: 48 failed / 100 passed over 148 runs on that bot, and 0 failures over ~1800 runs on every other MCP bot, so it's a Windows-Firefox timing issue, not a product one. Recent reds include push runs on main (b8627f95, f14e9f5c, dc82cd77) plus PRs fix(mcp): rebind page-registered WebMCP tools when the tab or frame changes #42821, docs(triage): also check previous similar issues and related PRs #42844, fix(clock): make Temporal.Now follow page.clock #42838, feat(firefox): roll to r1551 #42843, fix(chromium): report 204 subresource responses as finished #42834, docs(cli): do not suggest generating test scenarios in parallel #42833, fix(firefox): preserve response header field boundaries #42832 — all unrelated to this change.

  Run history on that bot (oldest → newest, 🟩 passed / 🟥 failed):

  🟥🟥🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟥🟩🟩🟩🟥🟩🟩🟥🟩🟩🟩🟥🟩🟥🟩🟥🟩🟩🟩🟩🟩🟥🟥🟥🟩🟥🟥

• An earlier push on this branch also saw [chromium] › mcp/cli-webmcp.spec.ts:162 › webmcp-call disambiguates duplicate tool names by frame fail; it passed in the latest run, so it's noise too.

Overall

The diff adds an includeShadow option to page.content() / frame.content() — docs, the protocol/validator plumbing, injectedScript.ts serialization, and one test in tests/page/page-set-content.spec.ts. Nothing there touches MCP CLI session lifecycle or idle-timeout handling, and the rest of CI is green (tests 1: 50478 passed, 0 failed; 8691 MCP tests passed).

_{Triaged by the Playwright bot - agent run}