Hack fix for terser problem

Author: hsubox76

packages/firestore/rollup.shared.js

@@ -145,6 +145,12 @@ const manglePrivatePropertiesOptions = {
     beautify: true
   },
   mangle: {
+    // Temporary hack fix for an issue where mangled code causes some downstream
+    // bundlers (Babel?) to confuse the same variable name in different scopes.
+    // This can be removed if the problem in the downstream library is fixed
+    // or if terser's mangler provides an option to avoid mangling everything
+    // that isn't a property.
+    reserved: ['_getProvider'],
     properties: {
       regex: /^__PRIVATE_/,
       // All JS Keywords are reserved. Although this should be taken cared of by
@@ -284,7 +290,12 @@ exports.es2017ToEs5Plugins = function (mangled = false) {
           comments: 'all',
           beautify: true
         },
-        mangle: true
+        // See comment above `manglePrivatePropertiesOptions`. This build did
+        // not have the identical variable name issue but we should be
+        // consistent.
+        mangle: {
+          reserved: ['_getProvider']
+        }
       }),
       sourcemaps()
     ];