Investigate reducing rrweb2 bundle size

[billyvg]

[AbhiPrasad]

Copying my comment from the upgrade PR: #8760 (comment)

I skimmed over the rrweb codebase, there's some improvements that can be upstreamed. Looking at https://unpkg.com/rrweb@2.0.0-alpha.4/dist/rrweb.min.js some easy ones are to use terser and minify private class properties and convert some classes to objects.

So immediate investigation points:

• Switch terser config and minify as much as possible
• Remove usage of TS enums
• Remove properties that aren't dynamic (like https://github.com/rrweb-io/rrweb/blob/64420c7e46abe84e63b1b4c1baa71ab30f7c9745/packages/rrdom/src/index.ts#L37C11-L37C35)
• Remove internal classes where possible (stuff like https://github.com/rrweb-io/rrweb/blob/64420c7e46abe84e63b1b4c1baa71ab30f7c9745/packages/rrdom-nodejs/src/document-nodejs.ts#L202 just seems uncesssary)
• Extract declarations like https://github.com/rrweb-io/rrweb/blob/64420c7e46abe84e63b1b4c1baa71ab30f7c9745/packages/rrweb/src/record/mutation.ts#L401C17-L402 into vars to save bytes

Longer term points:

• Identify what rrweb API we don't use and see if we can leverage build-time tools to tree-shake them out (like custom rollup plugin that aliases a certain files/functions).

[billyvg]

Ran rollup-bundle-analyzer on the replay package, here's what it looks like:

We could make iframe/canvas recording as an explicit opt-in so that its managers are tree-shaken when not used. This shaves off about ~10% from the replay bundle size (minified, 190KB -> 170KB) (Though I haven't tested if rrweb works without these managers).

[bruno-garcia]

With the work done by @mydea and https://sentry.engineering/blog/session-replay-sdk-bundle-size-optimizations
can we close this or more we can do?

[mydea]

Yes! 🎉