backend: remove file size measurement logic (#778)

Summary:
This logic isn’t currently useful to us. If we want this functionality,
we should consider using a Webpack plugin like `size-limit`. In the
meantime, this removes functionality from `scripts/backend.js`,
continuing on the path to #765.

Recommend reviewing with `-w`.

Test Plan:
Run `yarn backend` and `yarn backend --dry-run`, noting that each works.

wchargin-branch: backend-remove-file-sizes

scripts/backend.js

@@ -23,10 +23,6 @@ const formatWebpackMessages = require("react-dev-utils/formatWebpackMessages");
 const FileSizeReporter = require("react-dev-utils/FileSizeReporter");
 const printBuildError = require("react-dev-utils/printBuildError");
 
-const measureFileSizesBeforeBuild =
-  FileSizeReporter.measureFileSizesBeforeBuild;
-const printFileSizesAfterBuild = FileSizeReporter.printFileSizesAfterBuild;
-
 // These sizes are pretty large. We'll warn for bundles exceeding them.
 const WARN_AFTER_BUNDLE_GZIP_SIZE = 512 * 1024;
 const WARN_AFTER_CHUNK_GZIP_SIZE = 1024 * 1024;
@@ -35,15 +31,8 @@ const outputPath = process.argv.some((s) => s === "--dry-run" || s === "-n")
   ? tmp.dirSync({unsafeCleanup: true, prefix: "sourcecred-"}).name
   : paths.backendBuild;
 
-// First, read the current file sizes in build directory.
-// This lets us display how much they changed later.
-measureFileSizesBeforeBuild(outputPath)
-  .then((previousFileSizes) => {
-    // Start the webpack build
-    return build(previousFileSizes);
-  })
-  .then(
-    ({stats, previousFileSizes, warnings}) => {
+build().then(
+  ({stats, warnings}) => {
     if (warnings.length) {
       console.log(chalk.yellow("Compiled with warnings.\n"));
       console.log(warnings.join("\n\n"));
@@ -61,16 +50,6 @@ measureFileSizesBeforeBuild(outputPath)
       console.log(chalk.green("Compiled successfully.\n"));
     }
 
-      console.log("File sizes after gzip:\n");
-      printFileSizesAfterBuild(
-        stats,
-        previousFileSizes,
-        outputPath,
-        WARN_AFTER_BUNDLE_GZIP_SIZE,
-        WARN_AFTER_CHUNK_GZIP_SIZE
-      );
-      console.log();
-
     const buildFolder = path.relative(process.cwd(), outputPath);
     console.log(`Build completed; results in '${buildFolder}'.`);
   },
@@ -82,7 +61,7 @@ measureFileSizesBeforeBuild(outputPath)
 );
 
 // Create the backend build
-function build(previousFileSizes) {
+function build() {
   console.log("Building backend applications...");
 
   let compiler = webpack(config(outputPath));
@@ -116,7 +95,6 @@ function build(previousFileSizes) {
       }
       return resolve({
         stats,
-        previousFileSizes,
         warnings: messages.warnings,
       });
     });