Switch to using settings for android sdk location

Summary: A settings screen has been added where android home can be set. This changes the downstream code to use this value rather than the `env.PATH` variable.

Reviewed By: passy

Differential Revision: D17713288

fbshipit-source-id: 51551652c9c2f468e1117c18785123348e4b4576

src/chrome/DevicesButton.tsx

@@ -47,7 +47,6 @@ class DevicesButton extends Component<Props> {
     // On Linux, you must run the emulator from the directory it's in because
     // reasons ...
     whichPromise('emulator')
-      .catch(() => `${process.env.ANDROID_HOME || ''}/tools/emulator`)
       .then(emulatorPath => {
         if (emulatorPath) {
           const child = spawn(emulatorPath, [`@${name}`], {