Factor out realDevice [7/n]

Summary: `device.realDevice` was the escape hatch used in Sandy plugins to give access to device specific features like taking screenshots, clearing logs or accessing `adb`. Since in decapitated Flipper that won't be possible anymore (since plugins run in the client but device implementations on the server), all escape hatches have been bridged in this stack, and we can get of the `realDevice` interaction, by explicitly exposing those cases, which makes it type safe as well.

Reviewed By: passy

Differential Revision: D31079509

fbshipit-source-id: c9ec2e044d0dec0ccb1de287cf424907b198f818

desktop/plugins/public/reactdevtools/index.tsx

@@ -29,10 +29,6 @@ const DEV_TOOLS_NODE_ID = 'reactdevtools-out-of-react-node';
 const CONNECTED = 'DevTools connected';
 const DEV_TOOLS_PORT = 8097; // hardcoded in RN
 
-interface MetroDevice {
-  sendMetroCommand(command: string, params?: any): void;
-}
-
 function findGlobalDevTools(): Promise<string | undefined> {
   return new Promise((resolve) => {
     child_process.exec('npm root -g', (error, basePath) => {
@@ -64,10 +60,7 @@ enum ConnectionStatus {
 }
 
 export function devicePlugin(client: DevicePluginClient) {
-  const metroDevice: MetroDevice = client.device.realDevice;
-  if (!metroDevice.sendMetroCommand) {
-    throw new Error('Invalid metroDevice');
-  }
+  const metroDevice = client.device;
 
   const statusMessage = createState('initializing');
   const connectionStatus = createState<ConnectionStatus>(