Add tool to migrate logins between origins

App checks at startup for an existing session, if there isn't one,
it will start the tool to check for a login in the file:// origin.
If there is one, it will copy the login over to the vector://vector
origin.

In principle this could also be used to migrate logins between
other origins on the web if this were ever required.

This includes a minified copy of the browserified js-sdk with
a getAllEndToEndSessions() function added to the crypto store
(https://github.com/matrix-org/matrix-js-sdk/pull/812). This is
not great, but for a short-lived tool this seems better than
introducing more entry points into webpack only used for the
electron app.

src/vector/index.js

@@ -224,7 +224,16 @@ async function loadApp() {
     // set the platform for react sdk
     if (window.ipcRenderer) {
         console.log("Using Electron platform");
-        PlatformPeg.set(new ElectronPlatform());
+        const plaf = new ElectronPlatform();
+        PlatformPeg.set(plaf);
+
+        // Electron only: see if we need to do a one-time data
+        // migration
+        if (window.localStorage.getItem('mx_user_id') === null) {
+            console.log("Migrating session from old origin...");
+            await plaf.migrateFromOldOrigin();
+            console.log("Origin migration complete");
+        }
     } else {
         console.log("Using Web platform");
         PlatformPeg.set(new WebPlatform());

src/vector/platform/ElectronPlatform.js

@@ -224,6 +224,10 @@ export default class ElectronPlatform extends VectorBasePlatform {
         window.location.reload(false);
     }
 
+    async migrateFromOldOrigin() {
+        return this._ipcCall('origin_migrate');
+    }
+
     async _ipcCall(name, ...args) {
         const ipcCallId = ++this._nextIpcCallId;
         return new Promise((resolve, reject) => {

src/vector/platform/VectorBasePlatform.js

@@ -149,4 +149,12 @@ export default class VectorBasePlatform extends BasePlatform {
     getDefaultDeviceDisplayName(): string {
         return _t("Unknown device");
     }
+
+    /**
+     * Migrate account data from a previous origin
+     * Used only for the electron app
+     */
+    async migrateFromOldOrigin() {
+        return false;
+    }
 }