Moves some logic from native code to Dart:
- User-Agent header -> ExoPlayer user agent extraction logic (with TODOs for future improvements, based on implementation issues/questions I noticed while converting it).
- Asset -> URL lookup.
- Conversion of buffer position to the buffer range list required for the Dart event stream.

Also converts video format hint from strings to enums, which was missed in earlier Pigeon conversions. Using strings was the pre-Pigeon way of handling this kind of thing.

Part of flutter/flutter#172763

## Pre-Review Checklist

**Note**: The Flutter team is currently trialing the use of [Gemini Code Assist for GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code). Comments from the `gemini-code-assist` bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.

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Set myself as the CODEOWNER of Linux and Windows plugins, as I currently have the most experience with them.

Other minor changes to owners to reflect current owners.

Moves some logic from native code to Dart:
- Asset -> URL lookup.
- Conversion from native buffer range format (start+duration) to Dart range format (start+end).

Also does some minor native cleanup:
- Removes unnecessary state from `FVPVideoPlayerPlugin`; several registrar-vended objects were being stored, and later changes required storing the registrar itself, so now we can just get those from the registrar on demand.
- Removes nil player handling; the player can never return nil now.
- Removes `formatHint` from the Pigeon interface; it was only ever used on Android, so doesn't need to be sent across the language boundary.

Part of flutter/flutter#172763

## Pre-Review Checklist

**Note**: The Flutter team is currently trialing the use of [Gemini Code Assist for GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code). Comments from the `gemini-code-assist` bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.

[^1]: Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling.

flutter/flutter@46b097a...c3279ca

2025-07-30 [email protected] Roll Skia from 00765f238077 to da5a6704f8a3 (1 revision) (flutter/flutter#172966)
2025-07-30 [email protected] Roll Skia from 62476cd444d2 to 00765f238077 (3 revisions) (flutter/flutter#172955)
2025-07-30 [email protected] Roll Skia from 34693354289f to 62476cd444d2 (1 revision) (flutter/flutter#172950)
2025-07-30 [email protected] Roll Skia from f72bd01a49b1 to 34693354289f (1 revision) (flutter/flutter#172946)
2025-07-30 [email protected] [a11y] add RangeSlider to a11y test app as additional use-case (flutter/flutter#172922)
2025-07-30 [email protected] Roll Skia from a42898e5d622 to f72bd01a49b1 (21 revisions) (flutter/flutter#172944)
2025-07-29 [email protected] Fix SegmentedButton border doesn't reflect states (flutter/flutter#172754)
2025-07-29 [email protected] Fix documentation for FlutterEngineRunTask (flutter/flutter#172889)
2025-07-29 [email protected] Roll Fuchsia Linux SDK from tK_PAaLeo0pUxi8hv... to bQVQlLssTxxLjoDU0... (flutter/flutter#172925)
2025-07-29 [email protected] fix(scrollbar): Update padding type to EdgeInsetsGeometry (flutter/flutter#172056)
2025-07-29 [email protected] Refactor Android platform view code in advance of enabling HCPP on existing PV widgets (behind a flag) (flutter/flutter#170553)
2025-07-29 [email protected] Roll Packages from 6b2e34e to ed235d1 (4 revisions) (flutter/flutter#172905)
2025-07-29 [email protected] Add package PR triage note (flutter/flutter#172898)
2025-07-29 [email protected] Roll Skia from 409e1c7ba09b to a42898e5d622 (29 revisions) (flutter/flutter#172906)
2025-07-29 [email protected] Made `android_gradle_print_build_variants_test.dart` more robust (flutter/flutter#172910)
2025-07-29 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Reland licenses cpp switch (#172671)" (flutter/flutter#172912)
2025-07-29 [email protected] Fix Gemini Code Assist for GitHub config yaml (flutter/flutter#172887)
2025-07-29 [email protected] Marks Linux_android_emu_unstable android_defines_test to be unflaky (flutter/flutter#171856)

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