Fix emulator usage on linux

Summary: emulator isn't on the path in CI machines, but we already have ANDROID_HOME set so we can work out where it is.

Reviewed By: danielbuechele

Differential Revision: D15080422

fbshipit-source-id: 2c50a3de27909d2bfc82ea0210d06a0cc32357d7

src/chrome/DevicesButton.js

@@ -40,6 +40,7 @@ class DevicesButton extends Component<Props> {
     // On Linux, you must run the emulator from the directory it's in because
     // reasons ...
     whichPromise('emulator')
+      .catch(e => `${process.env.ANDROID_HOME || ''}/tools/emulator`)
       .then(emulatorPath => {
         const child = spawn(emulatorPath, [`@${name}`], {
           detached: true,