feat(keyboard): add pressSequence() for batched key presses

[SebTardif]

Summary

• Add keyboard.pressSequence(keys, options) to press an array of named keys in a single protocol round-trip
• Follows the same server-side batching pattern as the existing keyboard.type() for characters

Motivation

keyboard.type("hello") batches character-level key presses into a single protocol message, with all character events processed server-side. There is no equivalent for named keys (Space, ArrowDown, Enter, etc.).

When automating keyboard-driven interactions like drag-and-drop via accessibility patterns (Space to grab, Arrow keys to move, Space to drop) or multi-step form navigation, each keyboard.press() call requires a separate protocol round-trip:

// Current: 5 protocol round-trips
await page.keyboard.press('Space');
await page.keyboard.press('ArrowDown');
await page.keyboard.press('ArrowDown');
await page.keyboard.press('ArrowDown');
await page.keyboard.press('Space');

// New: 1 protocol round-trip
await page.keyboard.pressSequence(['Space', 'ArrowDown', 'ArrowDown', 'ArrowDown', 'Space'], { delay: 100 });

This is particularly relevant for:

• Keyboard-based drag-and-drop: Mouse-based dragTo() does not work with popular DnD libraries like react-beautiful-dnd and dnd-kit (#13855, #35749). The common workaround is keyboard-based reordering (Space/Arrow/Space), which requires multiple sequential keyboard.press() calls.

• AI browser agents: Tools like browser-use, Playwright MCP, and other automation agents rely heavily on keyboard sequences for form navigation. Each keyboard.press() call incurs protocol serialization + WebSocket frame + async scheduling overhead, which compounds in tight loops. See browser-use#4683 for a related request about faster input clearing.

• Remote automation: When Playwright connects to a remote browser via connect() or connect_over_cdp(), network latency amplifies per-call overhead from ~5-10ms locally to 50-200ms per call. A 5-key drag sequence goes from ~250ms to ~1s of pure overhead.

Unlike evaluateAll alternatives, this cannot be replicated with page.evaluate(): CDP keyboard events go through the browser's native input pipeline (Input.dispatchKeyEvent), triggering IME, contenteditable, autocomplete, and framework-specific event handlers that synthetic dispatchEvent() calls do not.

API

// Press keys sequentially with optional delay between presses
await page.keyboard.pressSequence(['Space', 'ArrowDown', 'Space'], { delay: 100 });

// Supports modifier combinations (same format as keyboard.press)
await page.keyboard.pressSequence(['ControlOrMeta+A', 'Backspace']);

// Empty array is a no-op
await page.keyboard.pressSequence([]);

Implementation

Follows the standard 6-step API addition process: docs, client, protocol, dispatcher, server, tests. The server-side pressSequence() method iterates the key array and delegates each press to the existing press() method, applying the delay between consecutive presses. 7 tests covering: basic sequencing, delay timing, empty/single arrays, modifier combos, event ordering, and invalid key error handling.

[pavelfeldman]

It is best to start with filing an issue, please see contributors' guide

[SebTardif]

Filed #40740 as requested.