Don't minify symbols in production builds (#28881)

This disables symbol renaming in production builds. The original
variable and function names are preserved. All other forms of
compression applied by Closure (dead code elimination, inlining, etc)
are unchanged — the final program is identical to what we were producing
before, just in a more readable form.

The motivation is to make it easier to debug React issues that only
occur in production — the same reason we decided to start shipping
sourcemaps in #28827 and #28827.

However, because most apps run their own minification step on their npm
dependencies, it's not necessary for us to minify the symbols before
publishing — it'll be handled the app, if desired.

This is the same strategy Meta has used to ship React for years. The
React build itself has unminified symbols, but they get minified as part
of Meta's regular build pipeline.

Even if an app does not minify their npm dependencies, gzip covers most
of the cost of symbol renaming anyway.

This saves us from having to ship sourcemaps, which means even apps that
don't have sourcemaps configured will be able to debug the React build
as easily as they would any other npm dependency.

DiffTrain build for [857ee8c](857ee8c)

compiled/facebook-www/REVISION

@@ -1 +1 @@
-ea26e38e33bffeba1ecc42688d7e8cd7e0da1c02
+857ee8cdf9af81bc94a7f04528fbda7fb2510eb4

compiled/facebook-www/unstable_server-external-runtime.js

@@ -1 +1,235 @@
-(function(){function e(e,t,n){t=document.getElementById(t);t.parentNode.removeChild(t);var r=document.getElementById(e);if(r){e=r.previousSibling;if(n)e.data="$!",r.setAttribute("data-dgst",n);else{n=e.parentNode;r=e.nextSibling;var i=0;do{if(r&&8===r.nodeType){var d=r.data;if("/$"===d)if(0===i)break;else i--;else"$"!==d&&"$?"!==d&&"$!"!==d||i++}d=r.nextSibling;n.removeChild(r);r=d}while(r);for(;t.firstChild;)n.insertBefore(t.firstChild,r);e.data="$"}e._reactRetry&&e._reactRetry()}}function t(t,n,r){for(var i=new Map,o=document,a,l,c=o.querySelectorAll("link[data-precedence],style[data-precedence]"),s=[],u=0;l=c[u++];)"not all"===l.getAttribute("media")?s.push(l):("LINK"===l.tagName&&d.set(l.getAttribute("href"),l),i.set(l.dataset.precedence,a=l));l=0;c=[];var m,f;for(u=!0;;){if(u){var v=r[l++];if(!v){u=!1;l=0;continue}var p=!1,b=0;var g=v[b++];if(f=d.get(g)){var h=f._p;p=!0}else{f=o.createElement("link");f.href=g;f.rel="stylesheet";for(f.dataset.precedence=m=v[b++];h=v[b++];)f.setAttribute(h,v[b++]);h=f._p=new Promise((function(e,t){f.onload=e;f.onerror=t}));d.set(g,f)}g=f.getAttribute("media");!h||"l"===h.s||g&&!window.matchMedia(g).matches||c.push(h);if(p)continue}else{f=s[l++];if(!f)break;m=f.getAttribute("data-precedence");f.removeAttribute("media")}p=i.get(m)||a;p===a&&(a=f);i.set(m,f);p?p.parentNode.insertBefore(f,p.nextSibling):(p=o.head,p.insertBefore(f,p.firstChild))}Promise.all(c).then(e.bind(null,t,n,""),e.bind(null,t,n,"Resource failed to load"))}function n(e){e=e.querySelectorAll("template");for(var t=0;t<e.length;t++)i(e[t])}function r(e){function t(e){for(var t=0;t<e.length;t++)for(var n=e[t].addedNodes,r=0;r<n.length;r++)n[r].parentNode&&i(n[r])}var n=new MutationObserver(t);n.observe(e,{childList:!0});window.addEventListener("DOMContentLoaded",(function(){t(n.takeRecords());n.disconnect()}))}function i(n){if(1===n.nodeType&&n.dataset){var r=n.dataset;if(null!=r.rxi){var i=r.dgst,d=r.msg,o=r.stck,a=r.cstck,l=document.getElementById(r.bid);l&&(r=l.previousSibling,r.data="$!",l=l.dataset,i&&(l.dgst=i),d&&(l.msg=d),o&&(l.stck=o),a&&(l.cstck=a),r._reactRetry&&r._reactRetry());n.remove()}else if(null!=r.rri)t(r.bid,r.sid,JSON.parse(r.sty)),n.remove();else if(null!=r.rci)e(r.bid,r.sid),n.remove();else if(null!=r.rsi){i=r.pid;d=document.getElementById(r.sid);i=document.getElementById(i);for(d.parentNode.removeChild(d);d.firstChild;)i.parentNode.insertBefore(d.firstChild,i);i.parentNode.removeChild(i);n.remove()}}}var d=new Map;(function(){addEventListener("submit",(function(e){if(!e.defaultPrevented){var t=e.target,n=e.submitter,r=t.action,i=n;if(n){var d=n.getAttribute("formAction");null!=d&&(r=d,i=null)}"javascript:throw new Error('React form unexpectedly submitted.')"===r&&(e.preventDefault(),i?(e=document.createElement("input"),e.name=i.name,e.value=i.value,i.parentNode.insertBefore(e,i),i=new FormData(t),e.parentNode.removeChild(e)):i=new FormData(t),e=t.ownerDocument||t,(e.$$reactFormReplay=e.$$reactFormReplay||[]).push(t,n,i))}}))})();window.$RC||(window.$RC=e,window.$RM=new Map);if(null!=document.body)"loading"===document.readyState&&r(document.body),n(document.body);else{var o=new MutationObserver((function(){null!=document.body&&("loading"===document.readyState&&r(document.body),n(document.body),o.disconnect())}));o.observe(document.documentElement,{childList:!0})}})();
+(function () {
+  function completeBoundary(suspenseBoundaryID, contentID, errorDigest) {
+    contentID = document.getElementById(contentID);
+    contentID.parentNode.removeChild(contentID);
+    var suspenseIdNode = document.getElementById(suspenseBoundaryID);
+    if (suspenseIdNode) {
+      suspenseBoundaryID = suspenseIdNode.previousSibling;
+      if (errorDigest)
+        (suspenseBoundaryID.data = "$!"),
+          suspenseIdNode.setAttribute("data-dgst", errorDigest);
+      else {
+        errorDigest = suspenseBoundaryID.parentNode;
+        suspenseIdNode = suspenseBoundaryID.nextSibling;
+        var depth = 0;
+        do {
+          if (suspenseIdNode && 8 === suspenseIdNode.nodeType) {
+            var data = suspenseIdNode.data;
+            if ("/$" === data)
+              if (0 === depth) break;
+              else depth--;
+            else ("$" !== data && "$?" !== data && "$!" !== data) || depth++;
+          }
+          data = suspenseIdNode.nextSibling;
+          errorDigest.removeChild(suspenseIdNode);
+          suspenseIdNode = data;
+        } while (suspenseIdNode);
+        for (; contentID.firstChild; )
+          errorDigest.insertBefore(contentID.firstChild, suspenseIdNode);
+        suspenseBoundaryID.data = "$";
+      }
+      suspenseBoundaryID._reactRetry && suspenseBoundaryID._reactRetry();
+    }
+  }
+  function completeBoundaryWithStyles(
+    suspenseBoundaryID,
+    contentID,
+    stylesheetDescriptors
+  ) {
+    for (
+      var precedences = new Map(),
+        thisDocument = document,
+        lastResource,
+        node,
+        nodes = thisDocument.querySelectorAll(
+          "link[data-precedence],style[data-precedence]"
+        ),
+        styleTagsToHoist = [],
+        i$0 = 0;
+      (node = nodes[i$0++]);
+
+    )
+      "not all" === node.getAttribute("media")
+        ? styleTagsToHoist.push(node)
+        : ("LINK" === node.tagName &&
+            resourceMap.set(node.getAttribute("href"), node),
+          precedences.set(node.dataset.precedence, (lastResource = node)));
+    node = 0;
+    nodes = [];
+    var precedence, resourceEl;
+    for (i$0 = !0; ; ) {
+      if (i$0) {
+        var stylesheetDescriptor = stylesheetDescriptors[node++];
+        if (!stylesheetDescriptor) {
+          i$0 = !1;
+          node = 0;
+          continue;
+        }
+        var avoidInsert = !1,
+          j = 0;
+        var href = stylesheetDescriptor[j++];
+        if ((resourceEl = resourceMap.get(href))) {
+          var attr = resourceEl._p;
+          avoidInsert = !0;
+        } else {
+          resourceEl = thisDocument.createElement("link");
+          resourceEl.href = href;
+          resourceEl.rel = "stylesheet";
+          for (
+            resourceEl.dataset.precedence = precedence =
+              stylesheetDescriptor[j++];
+            (attr = stylesheetDescriptor[j++]);
+
+          )
+            resourceEl.setAttribute(attr, stylesheetDescriptor[j++]);
+          attr = resourceEl._p = new Promise(function (resolve, reject) {
+            resourceEl.onload = resolve;
+            resourceEl.onerror = reject;
+          });
+          resourceMap.set(href, resourceEl);
+        }
+        href = resourceEl.getAttribute("media");
+        !attr ||
+          "l" === attr.s ||
+          (href && !window.matchMedia(href).matches) ||
+          nodes.push(attr);
+        if (avoidInsert) continue;
+      } else {
+        resourceEl = styleTagsToHoist[node++];
+        if (!resourceEl) break;
+        precedence = resourceEl.getAttribute("data-precedence");
+        resourceEl.removeAttribute("media");
+      }
+      avoidInsert = precedences.get(precedence) || lastResource;
+      avoidInsert === lastResource && (lastResource = resourceEl);
+      precedences.set(precedence, resourceEl);
+      avoidInsert
+        ? avoidInsert.parentNode.insertBefore(
+            resourceEl,
+            avoidInsert.nextSibling
+          )
+        : ((avoidInsert = thisDocument.head),
+          avoidInsert.insertBefore(resourceEl, avoidInsert.firstChild));
+    }
+    Promise.all(nodes).then(
+      completeBoundary.bind(null, suspenseBoundaryID, contentID, ""),
+      completeBoundary.bind(
+        null,
+        suspenseBoundaryID,
+        contentID,
+        "Resource failed to load"
+      )
+    );
+  }
+  function handleExistingNodes(target) {
+    target = target.querySelectorAll("template");
+    for (var i = 0; i < target.length; i++) handleNode(target[i]);
+  }
+  function installFizzInstrObserver(target) {
+    function handleMutations(mutations) {
+      for (var i = 0; i < mutations.length; i++)
+        for (
+          var addedNodes = mutations[i].addedNodes, j = 0;
+          j < addedNodes.length;
+          j++
+        )
+          addedNodes[j].parentNode && handleNode(addedNodes[j]);
+    }
+    var fizzInstrObserver = new MutationObserver(handleMutations);
+    fizzInstrObserver.observe(target, { childList: !0 });
+    window.addEventListener("DOMContentLoaded", function () {
+      handleMutations(fizzInstrObserver.takeRecords());
+      fizzInstrObserver.disconnect();
+    });
+  }
+  function handleNode(node_) {
+    if (1 === node_.nodeType && node_.dataset) {
+      var dataset = node_.dataset;
+      if (null != dataset.rxi) {
+        var errorDigest = dataset.dgst,
+          errorMsg = dataset.msg,
+          errorStack = dataset.stck,
+          errorComponentStack = dataset.cstck,
+          suspenseIdNode = document.getElementById(dataset.bid);
+        suspenseIdNode &&
+          ((dataset = suspenseIdNode.previousSibling),
+          (dataset.data = "$!"),
+          (suspenseIdNode = suspenseIdNode.dataset),
+          errorDigest && (suspenseIdNode.dgst = errorDigest),
+          errorMsg && (suspenseIdNode.msg = errorMsg),
+          errorStack && (suspenseIdNode.stck = errorStack),
+          errorComponentStack && (suspenseIdNode.cstck = errorComponentStack),
+          dataset._reactRetry && dataset._reactRetry());
+        node_.remove();
+      } else if (null != dataset.rri)
+        completeBoundaryWithStyles(
+          dataset.bid,
+          dataset.sid,
+          JSON.parse(dataset.sty)
+        ),
+          node_.remove();
+      else if (null != dataset.rci)
+        completeBoundary(dataset.bid, dataset.sid), node_.remove();
+      else if (null != dataset.rsi) {
+        errorDigest = dataset.pid;
+        errorMsg = document.getElementById(dataset.sid);
+        errorDigest = document.getElementById(errorDigest);
+        for (errorMsg.parentNode.removeChild(errorMsg); errorMsg.firstChild; )
+          errorDigest.parentNode.insertBefore(errorMsg.firstChild, errorDigest);
+        errorDigest.parentNode.removeChild(errorDigest);
+        node_.remove();
+      }
+    }
+  }
+  var resourceMap = new Map();
+  (function () {
+    addEventListener("submit", function (event) {
+      if (!event.defaultPrevented) {
+        var form = event.target,
+          submitter = event.submitter,
+          action = form.action,
+          formDataSubmitter = submitter;
+        if (submitter) {
+          var submitterAction = submitter.getAttribute("formAction");
+          null != submitterAction &&
+            ((action = submitterAction), (formDataSubmitter = null));
+        }
+        "javascript:throw new Error('React form unexpectedly submitted.')" ===
+          action &&
+          (event.preventDefault(),
+          formDataSubmitter
+            ? ((event = document.createElement("input")),
+              (event.name = formDataSubmitter.name),
+              (event.value = formDataSubmitter.value),
+              formDataSubmitter.parentNode.insertBefore(
+                event,
+                formDataSubmitter
+              ),
+              (formDataSubmitter = new FormData(form)),
+              event.parentNode.removeChild(event))
+            : (formDataSubmitter = new FormData(form)),
+          (event = form.ownerDocument || form),
+          (event.$$reactFormReplay = event.$$reactFormReplay || []).push(
+            form,
+            submitter,
+            formDataSubmitter
+          ));
+      }
+    });
+  })();
+  window.$RC || ((window.$RC = completeBoundary), (window.$RM = new Map()));
+  if (null != document.body)
+    "loading" === document.readyState &&
+      installFizzInstrObserver(document.body),
+      handleExistingNodes(document.body);
+  else {
+    var domBodyObserver = new MutationObserver(function () {
+      null != document.body &&
+        ("loading" === document.readyState &&
+          installFizzInstrObserver(document.body),
+        handleExistingNodes(document.body),
+        domBodyObserver.disconnect());
+    });
+    domBodyObserver.observe(document.documentElement, { childList: !0 });
+  }
+})();