Iterated on Webpack configs until I got the inline and shell packages seemingly working

packages/react-devtools-shared/babel.config.js

@@ -0,0 +1,46 @@
+const chromeManifest = require('../react-devtools-extensions/chrome/manifest.json');
+const firefoxManifest = require('../react-devtools-extensions/firefox/manifest.json');
+
+const minChromeVersion = parseInt(chromeManifest.minimum_chrome_version, 10);
+const minFirefoxVersion = parseInt(
+  firefoxManifest.applications.gecko.strict_min_version,
+  10,
+);
+validateVersion(minChromeVersion);
+validateVersion(minFirefoxVersion);
+
+function validateVersion(version) {
+  if (version > 0 && version < 200) {
+    return;
+  }
+  throw new Error('Suspicious browser version in manifest: ' + version);
+}
+
+module.exports = api => {
+  const isTest = api.env('test');
+  const targets = {};
+  if (isTest) {
+    targets.node = 'current';
+  } else {
+    targets.chrome = minChromeVersion.toString();
+    targets.firefox = minFirefoxVersion.toString();
+
+    // This targets RN/Hermes.
+    targets.ie = '11';
+  }
+  const plugins = [
+    ['@babel/plugin-transform-flow-strip-types'],
+    ['@babel/plugin-proposal-class-properties', {loose: false}],
+  ];
+  if (process.env.NODE_ENV !== 'production') {
+    plugins.push(['@babel/plugin-transform-react-jsx-source']);
+  }
+  return {
+    plugins,
+    presets: [
+      ['@babel/preset-env', {targets}],
+      '@babel/preset-react',
+      '@babel/preset-flow',
+    ],
+  };
+};

packages/react-devtools-shared/package.json

@@ -3,6 +3,7 @@
   "name": "react-devtools-shared",
   "version": "0.0.0",
   "dependencies": {
+    "@babel/runtime": "^7.0.0",
     "@reach/menu-button": "^0.1.17",
     "@reach/tooltip": "^0.2.2",
     "clipboard-js": "^0.3.6",

packages/react-devtools-shared/src/devtools/views/DevTools.js

@@ -97,8 +97,8 @@ export default function DevTools({
 
   const viewElementSource = useMemo(
     () => ({
-      canViewElementSourceFunction,
-      viewElementSourceFunction,
+      canViewElementSourceFunction: canViewElementSourceFunction || null,
+      viewElementSourceFunction: viewElementSourceFunction || null,
     }),
     [canViewElementSourceFunction, viewElementSourceFunction],
   );

packages/react-devtools-shared/src/devtools/views/ErrorBoundary.js

@@ -51,7 +51,7 @@ export default class ErrorBoundary extends Component<Props, State> {
     let bugURL = process.env.GITHUB_URL;
     if (bugURL) {
       const title = `Error: "${errorMessage || ''}"`;
-      const label = '😭 bug';
+      const label = 'Component: Developer Tools';
 
       let body = '<!-- please provide repro information here -->\n';
       body += '\n---------------------------------------------';

packages/react-devtools-shared/src/devtools/views/Profiler/SidebarSelectedFiberInfo.js

@@ -30,7 +30,8 @@ export default function SidebarSelectedFiberInfo(_: Props) {
   });
 
   const listItems = [];
-  for (let i = 0; i < commitIndices.length; i++) {
+  let i = 0;
+  for (i = 0; i < commitIndices.length; i++) {
     const commitIndex = commitIndices[i];
 
     const {duration, timestamp} = profilerStore.getCommitData(