Simple approach for minifying blazor.*.js on release builds. Fixes #1003

Later we might want to emit both min and non-min variants of the file, when there is some way for developers to control which one they use

src/Microsoft.AspNetCore.Blazor.Browser.JS/Microsoft.AspNetCore.Blazor.Browser.JS.csproj

@@ -26,7 +26,8 @@
 
   <Target Name="RunWebpack" AfterTargets="ResolveReferences" Inputs="@(WebpackInputs)" Outputs="dist\blazor.webassembly.js" DependsOnTargets="EnsureNpmRestored">
     <RemoveDir Directories="dist" />
-    <Exec Command="npm run build" />
+    <Exec Command="npm run build:debug" Condition="'$(Configuration)' == 'Debug'" />
+    <Exec Command="npm run build:production" Condition="'$(Configuration)' != 'Debug'" />
     <ItemGroup>
       <EmbeddedResource Include="dist\blazor.webassembly.js" LogicalName="blazor./blazor.webassembly.js" />
     </ItemGroup>

src/Microsoft.AspNetCore.Blazor.Browser.JS/package.json

@@ -4,7 +4,8 @@
   "description": "",
   "main": "index.js",
   "scripts": {
-    "build": "webpack --mode development",
+    "build:debug": "webpack --mode development",
+    "build:production": "webpack --mode production",
     "test": "echo \"Error: no test specified\" && exit 1"
   },
   "devDependencies": {

src/Microsoft.AspNetCore.Blazor.Browser.JS/webpack.config.js

@@ -1,9 +1,9 @@
 const path = require('path');
 const webpack = require('webpack');
 
-module.exports = {
+module.exports = (env, args) => ({
     resolve: { extensions: ['.ts', '.js'] },
-    devtool: 'inline-source-map',
+    devtool: args.mode === 'development' ? 'inline-source-map' : 'none',
     module: {
         rules: [{ test: /\.ts?$/, loader: 'ts-loader' }]
     },
@@ -11,4 +11,4 @@ module.exports = {
         'blazor.webassembly': './src/Boot.WebAssembly.ts',
     },
     output: { path: path.join(__dirname, '/dist'), filename: '[name].js' }
-};
+});