This was mostly a side-effect of re-enabling source maps using inline-source-map, but there were some other interesting things happening, notably all of code_intelligence.tsx and its dependencies (react-dom, highlight.js, popper...) being pulled into the background page and options bundles
I made two main changes:
A slight refactor in sentry/index.ts, to avoid calling determineCodeHost() in the background and options pages, which is pointless anyway and leads to a bunch of content script-specific stuff being bundled in.
Switching to inline-cheap-module-source-map for prod as well. This yields much smaller bundle sizes than inline-source-map, will still allow for correct stacktrace mapping in Sentry, and doesn't degrade the debugging experience (this is already what we used in dev mode).
This gets us under the 4mb limit, but there are further opportunities to optimize:
The bulk of the size of the background page bundle is the inlined extension host worker. Since we anyway use it as a separate bundle in the integrations, we could do the same thing in the background page (instantiating it as new Worker(browser.runtime.getURL('js/extensionHostWorker.bundle.js')) and avoid not only bundling it, but also compiling it multiple times, for the background, phabricator and integrations entry points.
The bulk of the size of the injected JS bundle is dependencies. Maybe there's some fat-trimming we could do there.
