Issue 1:
A recent update to the React Developer Tools Chrome Extension looks like it has a build issue.

The current behaviour

Chrome console is reporting

DevTools failed to load SourceMap: Could not load content for chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/injectGlobalHook.js.map: HTTP error: status code 404, net::ERR_UNKNOWN_URL_SCHEME

Looking at the map file it contains a lot of references to local paths on @bvaughn's computer.

{"version":3,"sources":["webpack:///webpack/bootstrap","webpack:////Users/bvaughn/Documents/git/react.alt2/build/node_modules/react/index.js","webpack:///../react-devtools-shared/src/types.js","webpack:////Users/bvaughn/Documents/git/react.alt2/build/node_modules/react-is/index.js","webpack:///../react-devtools-shared/src/hook.js","webpack:///./src/injectGlobalHook.js","webpack:////Users/bvaughn/Documents/git/react.alt2/node_modules/clipboard-js/clipboard.js","webpack:///../shared/ReactSymbols.js","webpack:///../react-devtools-shared/src/utils.js","webpack:///../react-devtools-shared/node_modules/semver/semver.js","webpack:///../react-devtools-shared/src/constants.js","webpack:////Users/bvaughn/Documents/git/react.alt2/node_modules/object-assign/index.js","webpack:////Users/bvaughn/Documents/git/react.alt2/node_modules/lru-cache/index.js","webpack:///../shared/ConsolePatchingDev.js","webpack:///../react-devtools-shared/src/backend/DevToolsComponentStackFrame.js","webpack:///../react-devtools-shared/src/backend/DevToolsFiberComponentStack.js","webpack:///../react-devtools-shared/src/backend/console.js","webpack:///../react-devtools-shared/src/backend/utils.js","webpack:///../react-devtools-shared/src/backend/renderer.js","webpack:///../react-devtools-shared/src/backend/ReactSymbols.js","webpack:////Users/bvaughn/Documents/git/react.alt2/node_modules/process/browser.js","webpack:////Users/bvaughn/Documents/git/react.alt2/node_modules/lru-cache/node_modules/yallist/yallist.js","webpack:////Users/bvaughn/Documents/git/react.alt2/node_modules/lru-cache/node_modules/yallist/iterator.js","webpack:////Users/bvaughn/Documents/git/react.alt2/build/node_modules/react-is/cjs/react-is.production.min.js","webpack:///../react-devtools-shared/src/devtools/views/root.css","webpack:////Users/bvaughn/Documents/git/react.alt2/build/node_modules/react/cjs/react.production.min.js","webpack:////Users/bvaughn/Documents/git/react.alt2/build/node_modules/react-debug-tools/index.js","webpack:////Users/bvaughn/Documents/git/react.alt2/build/node_modules/react-debug-tools/cjs/react-debug-tools.production.min.js","webpack:////Users/bvaughn/Documents/git/react.alt2/node_modules/error-stack-parser/error-stack-parser.js","webpack:////Users/bvaughn/Documents/git/react.alt2/node_modules/stackframe/stackframe.js","webpack:////Users/bvaughn/Documents/git/react.alt2/node_modules/nullthrows/nullthrows.js","webpack:///../react-devtools-shared/src/storage.js","webpack:///../react-devtools-shared/src/hydration.js"],"names":["process","module","exports","require","ElementTypeClass","ElementTypeContext","ElementTypeFunction","ElementTypeForwardRef","ElementTypeHostComponent","ElementTypeMemo","ElementTypeOtherOrUnknown","ElementTypeProfiler","ElementTypeRoot","ElementTypeSu

The expected behaviour

No Chrome message complaining about the SourceMap

Issue 2:
In extjs-reactor we use some react internal methods like mountComponent, unmountComponent, and receiveComponent, as well as the ReactMultiChild mixin to defer rendering to Ext JS. This interface was very helpful for anyone looking to make generic JS component libraries work in React (as opposed to those built specifically for React).

Is there an equivalent/alternative way to control the mounting of a component in the new Fiber architecture?

If it helps, here is the code that references the React internal methods:

https://github.com/sencha/extjs-reactor/blob/master/packages/reactor/src/ExtJSComponent.js