Improve source maps (#9101)

Our source maps were being corrupted during minification, because the
`gulp-terser-js` plugin we were using didn't account for the existence
of sourcemaps in the input. A configuration option to allow the input
of sourcemaps was added in v5.2.0. The plugin has been updated, and we
now use this option.

Previously the generated sourcemaps had an invalid entry in the
"sources" array, with the filename of the bundle itself. This was not a
real source. After this change, this invalid source is no longer
present.

development/build/scripts.js

@@ -206,6 +206,9 @@ function createScriptTasks ({ browserPlatforms, livereload }) {
             mangle: {
               reserved: [ 'MetamaskInpageProvider' ],
             },
+            sourceMap: {
+              content: true,
+            },
           }))
       }
 

package.json

@@ -236,7 +236,7 @@
     "gulp-sass": "^4.0.0",
     "gulp-sourcemaps": "^2.6.0",
     "gulp-stylelint": "^13.0.0",
-    "gulp-terser-js": "^5.0.0",
+    "gulp-terser-js": "^5.2.2",
     "gulp-watch": "^5.0.1",
     "gulp-zip": "^4.0.0",
     "jsdom": "^11.2.0",

yarn.lock

@@ -12979,14 +12979,14 @@ gulp-stylelint@^13.0.0:
     strip-ansi "^6.0.0"
     through2 "^3.0.1"
 
-gulp-terser-js@^5.0.0:
-  version "5.0.0"
-  resolved "https://registry.yarnpkg.com/gulp-terser-js/-/gulp-terser-js-5.0.0.tgz#b570bb14e9c836aab78d633411073af0df8ca514"
-  integrity sha512-X5bduLqvRdX1RwUJmdm1J+HZu85gfIKkmDK95J6AAfXd4W/oYANt82gmIMZfhUGEmLm6e6xtKGsfTW6c0BRWnQ==
+gulp-terser-js@^5.2.2:
+  version "5.2.2"
+  resolved "https://registry.yarnpkg.com/gulp-terser-js/-/gulp-terser-js-5.2.2.tgz#3d93db9b2b83f35dfcc5b209af6b1762756eb6a3"
+  integrity sha512-4ull0HzTWeWjRPiGmAFmdhRcEDOG+r7aXivNHOBQzElLzMaeVKQwmCPDi2juBzUUkjAkPkKb1jHVoJN/PKTvcA==
   dependencies:
-    object-assign "^4.1.1"
     plugin-error "^1.0.1"
-    terser "^4.1.4"
+    source-map "^0.7.3"
+    terser "^4.6.12"
     through2 "^3.0.1"
     vinyl-sourcemaps-apply "^0.2.1"
 
@@ -25703,10 +25703,10 @@ terser@^4.1.2, terser@^4.4.3:
     source-map "~0.6.1"
     source-map-support "~0.5.12"
 
-terser@^4.1.4:
-  version "4.3.1"
-  resolved "https://registry.yarnpkg.com/terser/-/terser-4.3.1.tgz#09820bcb3398299c4b48d9a86aefc65127d0ed65"
-  integrity sha512-pnzH6dnFEsR2aa2SJaKb1uSCl3QmIsJ8dEkj0Fky+2AwMMcC9doMqLOQIH6wVTEKaVfKVvLSk5qxPBEZT9mywg==
+terser@^4.6.12:
+  version "4.8.0"
+  resolved "https://registry.yarnpkg.com/terser/-/terser-4.8.0.tgz#63056343d7c70bb29f3af665865a46fe03a0df17"
+  integrity sha512-EAPipTNeWsb/3wLPeup1tVPaXfIaU68xMnVdPafIL1TV05OhASArYyIfFvnvJCNrR2NIOvDVNNTFRa+Re2MWyw==
   dependencies:
     commander "^2.20.0"
     source-map "~0.6.1"