feat(@angular/cli): name lazy chunks

Before:
```
$ ng build --no-progress
Hash: ff03df269349b817eef4
Time: 11202ms
chunk    {0} 0.chunk.js, 0.chunk.js.map 1.61 kB {1} {3} [rendered]
chunk    {1} 1.chunk.js, 1.chunk.js.map 1.46 kB {0} {3} [rendered]
chunk    {2} polyfills.bundle.js, polyfills.bundle.js.map (polyfills) 160 kB {6} [initial] [rendered]
chunk    {3} main.bundle.js, main.bundle.js.map (main) 6.38 kB {5} [initial] [rendered]
chunk    {4} styles.bundle.js, styles.bundle.js.map (styles) 10.5 kB {6} [initial] [rendered]
chunk    {5} vendor.bundle.js, vendor.bundle.js.map (vendor) 2.16 MB [initial] [rendered]
chunk    {6} inline.bundle.js, inline.bundle.js.map (inline) 0 bytes [entry] [rendered]
```

After:
```
$ ng build --no-progress
Hash: 2bc12a89f40f3b4818b5
Time: 9613ms
chunk {feature.module} feature.module.chunk.js, feature.module.chunk.js.map 1.46 kB {lazy.module} {main} [rendered]
chunk {inline} inline.bundle.js, inline.bundle.js.map (inline) 0 bytes [entry] [rendered]
chunk {lazy.module} lazy.module.chunk.js, lazy.module.chunk.js.map 1.61 kB {feature.module} {main} [rendered]
chunk {main} main.bundle.js, main.bundle.js.map (main) 6.38 kB {vendor} [initial] [rendered]
chunk {polyfills} polyfills.bundle.js, polyfills.bundle.js.map (polyfills) 160 kB {inline} [initial] [rendered]
chunk {styles} styles.bundle.js, styles.bundle.js.map (styles) 10.5 kB {inline} [initial] [rendered]
chunk {vendor} vendor.bundle.js, vendor.bundle.js.map (vendor) 2.16 MB [initial] [rendered]
```

Fix angular#6700

packages/@angular/cli/models/webpack-configs/common.ts

@@ -1,6 +1,7 @@
 import * as webpack from 'webpack';
 import * as path from 'path';
 import { GlobCopyWebpackPlugin } from '../../plugins/glob-copy-webpack-plugin';
+import { NamedLazyChunksWebpackPlugin } from '../../plugins/named-lazy-chunks-webpack-plugin';
 import { extraEntryParser, getOutputHashFormat } from './utils';
 import { WebpackConfigOptions } from '../webpack-config';
 
@@ -109,7 +110,8 @@ export function getCommonConfig(wco: WebpackConfigOptions) {
       ].concat(extraRules)
     },
     plugins: [
-      new webpack.NoEmitOnErrorsPlugin()
+      new webpack.NoEmitOnErrorsPlugin(),
+      // new NamedLazyChunksWebpackPlugin(),
     ].concat(extraPlugins),
     node: {
       fs: 'empty',

packages/@angular/cli/plugins/named-lazy-chunks-webpack-plugin.ts

@@ -0,0 +1,38 @@
+import * as webpack from 'webpack';
+
+// This is just a wrapper around webpack.NamedChunksPlugin to prevent name collisions.
+export class NamedLazyChunksWebpackPlugin {
+  constructor() {
+    const nameMap = new Map();
+    // Append a dot and number if the name already exists.
+    const getNextName = (baseName: string) => {
+      let num: number | null = null;
+      const name = () => num !== null ? `${baseName}.${num}` : baseName;
+      while (nameMap.has(name())) {
+        num = num ? num++ : 0;
+      }
+      nameMap.set(name(), true);
+      return name();
+    };
+
+    return new (webpack as any).NamedChunksPlugin(function (chunk: any) {
+      // Entry chunks have a name already, use it.
+      if (chunk.name) {
+        return chunk.name;
+      }
+
+      // Try to figure out if it's a lazy loaded route.
+      if (chunk.blocks
+        && chunk.blocks.length > 0
+        && chunk.blocks[0].dependencies
+        && chunk.blocks[0].dependencies.length > 0
+        && chunk.blocks[0].dependencies[0].lazyRouteChunkName
+      ) {
+        // lazyRouteChunkName was added by @ngtools/webpack.
+        return getNextName(chunk.blocks[0].dependencies[0].lazyRouteChunkName);
+      }
+
+      return null;
+    });
+  }
+}

packages/@ngtools/webpack/src/plugin.ts

@@ -310,7 +310,11 @@ export class AotPlugin implements Tapable {
               .map((key) => {
                 const value = this._lazyRoutes[key];
                 if (value !== null) {
-                  return new ContextElementDependency(value, key);
+                  const dep = new ContextElementDependency(value, key);
+                  // lazyRouteChunkName is used by webpack.NamedChunksPlugin to give the
+                  // lazy loaded chunk a name.
+                  dep.lazyRouteChunkName = path.basename(key, '.ts');
+                  return dep;
                 } else {
                   return null;
                 }