Replace closure compiler plugin with official one

Replace webpack-closure-compiler (deprecated) with closure-webpack-plugin,
which is official closure plugin.
Also, reworked CI.

webpack.base.js

@@ -0,0 +1,131 @@
+const path = require('path');
+const ClosurePlugin = require('closure-webpack-plugin');
+const { CleanWebpackPlugin } = require('clean-webpack-plugin');
+const CopyWebpackPlugin = require('copy-webpack-plugin');
+const HtmlWebpackPlugin = require('html-webpack-plugin');
+const { DefinePlugin } = require('webpack');
+const { exec } = require('child_process');
+const fs = require('fs');
+
+
+function makeClosureCompiler() {
+    const externDir = path.join(__dirname, "externs");
+    const externs = [
+        path.join(externDir, "googleAnalytics.js"),
+        path.join(externDir, "performance.js"),
+        path.join(externDir, "webassembly.js")
+    ];
+
+    var flags = {
+        compilation_level: "ADVANCED",
+        externs: externs
+    };
+
+    return new ClosurePlugin({mode: 'STANDARD'}, flags);
+}
+
+
+class VersionInfoPlugin {
+    constructor(options = {}) {
+        if (options.filename == void 0) {
+            throw new Error('[VersionInfoPlugin] filename should be set');
+        }
+        this.options = options;
+    }
+
+    apply(compiler) {
+        const plugin = { name: 'VersionInfoPlugin' }
+        compiler.hooks.afterEmit.tapAsync(plugin, (compilation, callback) => {
+            exec('git describe --tags --always', (error, stdout, stderr) => {
+                if (error) {
+                    compilation.errors.push(error);
+                    callback();
+                    return;
+                }
+
+                var version_info = `version: ${stdout.trim()}\ntime: ${new Date().toISOString()}\n`;
+                if (process.env.TRAVIS) {
+                    version_info += `build id: TRAVIS ${process.env.TRAVIS_JOB_NUMBER} (${process.env.TRAVIS_BUILD_ID})\n`;
+                }
+
+                const filename = path.join(compiler.options.output.path, this.options.filename);
+
+                fs.writeFile(filename, version_info, (err) => {
+                    if (err) {
+                        compilation.errors.push(err);
+                    }
+                    callback();
+                })
+            });
+        });
+    }
+}
+
+function getWebpackConfig(production, gtag) {
+    var webpackMode;
+
+    production = (typeof(production) === 'undefined') ? false : production;
+    gtag = (typeof(gtag) === 'undefined') ? "" : gtag;
+
+    var plugins = [
+        new CleanWebpackPlugin(),
+        new CopyWebpackPlugin([
+            {
+                from: 'assets/bootstrap.min.css',
+                to: 'assets/'
+            }
+        ]),
+        new DefinePlugin({
+            GOOGLE_ANALYTICS_TAG: JSON.stringify(gtag)
+        }),
+        new HtmlWebpackPlugin({
+            minify: {
+                collapseWhitespace: true,
+                conservativeCollapse: true,
+                removeComments: true
+            },
+            inject: true,
+            template: 'html/index.html'
+        }),
+        new VersionInfoPlugin({filename: 'version-info.txt'})
+    ];
+
+    if (production) {
+        plugins.push(makeClosureCompiler());
+        webpackMode = "production";
+    } else {
+        webpackMode = "development";
+    }
+
+    return {
+        entry: "./src/ui.ts",
+        output: {
+            filename: "assets/bundle.[hash].js",
+            path: path.join(__dirname, "dist")
+        },
+        plugins: plugins,
+        optimization: {
+            concatenateModules: false
+        },
+        devtool: "source-map",
+        devServer: {
+            contentBase: path.join(__dirname, "dist"),
+            port: 9000
+        },
+        resolve: {
+            extensions: ['.ts', '.tsx', '.js']
+        },
+        mode: webpackMode,
+        module: {
+            rules: [
+                {
+                    test: /\.ts$/,
+                    exclude: /node_modules/,
+                    use: [{loader: 'ts-loader', options: {transpileOnly: true}}]
+                }
+            ]
+        }
+    }
+}
+
+exports.getWebpackConfig = getWebpackConfig