Update Android Studio code style instructions.

This has been a source of confusion for several developers since the
old instructions are ambiguous about the last step.

BUG=

Review-Url: https://codereview.chromium.org/2864433005
Cr-Commit-Position: refs/heads/master@{#469392}

docs/android_studio.md

@@ -92,7 +92,7 @@ includes `R.java`).
 * If you ever need to reset it: `rm -r ~/.AndroidStudio*/`
 * Import Android style settings:
     * Help -> Find Action -> "Code Style" (settings) -> Java ->
-      Manage -> Import
+      Manage -> Import -> select "Intellij IDEA code style XML" -> OK
         * Select `tools/android/android_studio/ChromiumStyle.xml`
 * Turn on automatic import:
     * Help -> Find Action -> "Auto Import"