Update android studio doc about formatting commits.

docs/android_studio.md

 # Android Studio
 
 [TOC]
 
 ## Usage
 
 Make sure you have followed
 [android build instructions](android_build_instructions.md) already.
 
 ```shell
@@ skipping 83 matching lines @@
     * Help -> Find Action -> "Code Style" (settings) -> Java ->
       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"
         * Tick all the boxes under "Java" and change the dropdown to "All".
 * Turn on documentation on mouse hover:
     * Help -> Find Action -> "Show quick documentation on mouse move"
 * Turn on line numbers:
     * Help -> Find Action -> "Show line numbers"
+* Format changed files (Useful for changes made by running code inspection):
+    * Set up version control
+        * File -> Settings -> Version Control
+        * Add src directories
+    * Commit changes and reformat
+        * Help -> Find Action -> "Commit Changes"
+        * Check "Reformat code" & "Optimize imports" and commit
 
 ### Useful Shortcuts
 
 * `Shift - Shift`: Search to open file or perform IDE action
 * `Ctrl + N`: Jump to class
 * `Ctrl + Shift + T`: Jump to test
 * `Ctrl + Shift + N`: Jump to file
 * `Ctrl + F12`: Jump to method
 * `Ctrl + G`: Jump to line
 * `Shift + F6`: Rename variable
@@ skipping 31 matching lines @@
 [here](/docs/android_debugging_instructions.md#Android-Studio)).
 * Import resolution and refactoring across all modules.
 * Correct lint and AndroidManifest when only one target is specified.
 
 ### What doesn't work (yet) ([crbug](https://bugs.chromium.org/p/chromium/issues/detail?id=620034))
 
 * Gradle being aware of assets.
 * Layout editor.
 * Add support for native code editing.
 * Make the "Make Project" button work correctly.