Add polyfill for AbortController (#7157)

The AbortController is used in both the background and the UI. Support
for AbortController was added to Chrome in version 66, which is above
our minimum supported version.

I did consider increasing the minimum Chrome version to 66, but we have
a decent number of users still on Chrome 65 unfortunately.

app/scripts/background.js

@@ -5,6 +5,9 @@
 // this needs to run before anything else
 require('./lib/setupFetchDebugging')()
 
+// polyfills
+import 'abortcontroller-polyfill/dist/polyfill-patch-fetch'
+
 const urlUtil = require('url')
 const endOfStream = require('end-of-stream')
 const pump = require('pump')

app/scripts/ui.js

@@ -1,3 +1,6 @@
+// polyfills
+import 'abortcontroller-polyfill/dist/polyfill-patch-fetch'
+
 const PortStream = require('extension-port-stream')
 const { getEnvironmentType } = require('./lib/util')
 const { ENVIRONMENT_TYPE_NOTIFICATION, ENVIRONMENT_TYPE_FULLSCREEN, ENVIRONMENT_TYPE_POPUP } = require('./lib/enums')

package.json

@@ -53,6 +53,7 @@
     "@sentry/browser": "^4.1.1",
     "@zxing/library": "^0.8.0",
     "abi-decoder": "^1.2.0",
+    "abortcontroller-polyfill": "^1.3.0",
     "asmcrypto.js": "^2.3.2",
     "await-semaphore": "^0.1.1",
     "bignumber.js": "^4.1.0",
@@ -180,7 +181,6 @@
     "@storybook/addon-info": "^5.1.1",
     "@storybook/addon-knobs": "^3.4.2",
     "@storybook/react": "^5.1.1",
-    "abortcontroller-polyfill": "^1.3.0",
     "addons-linter": "^1.10.0",
     "babel-eslint": "^10.0.2",
     "babelify": "^10.0.0",