Correct some details in the instructions for modifying TTS engine.

docs/accessibility/patts.md

Index: docs/accessibility/patts.md
diff --git a/docs/accessibility/patts.md b/docs/accessibility/patts.md
index 5a7fce52891beaf0ce8ee90149aa5873d16f6eeb..c51b911c73699e25f222529d7c684d0398415104 100644
--- a/docs/accessibility/patts.md
+++ b/docs/accessibility/patts.md
@@ -33,22 +33,28 @@ Before you can make changes to PATTS, the first thing you need to run
 (from the chroot) is call cros_workon with two relevant ebuilds:
 
 ```
-cros_workon --board=$BOARD start chromeos-assets
+cros_workon --board=$BOARD start chromiumos-assets

[dmazzoni, 2017/02/25 01:56:18]

Is it possible the difference has to do with whether you have the
internal or external sources checked out? Or did this change recently
maybe?

I'm not disputing this worked for you, I'm just trying to better
understand it...

[Wez, 2017/02/25 02:06:52]

That's a good question; I did indeed just follow the public instructions, so
quite possibly.

 cros_workon --board=$BOARD start common-assets
 ```
 
-Next, make sure you're in the platform/assets directory and run
-```repo start``` and create a branch.
+From outside the root, from anywhere under your top-level ```<repo-dir>```, pull down the relevant sources:
 
 ```
-cd platform/assets
+repo sync
+```
+
+Again, outside the root, make sure you're in the ```<repo-dir>/src/platform/assets``` directory and run
+```repo start``` to create a branch:
+
+```
+cd src/platform/assets
 repo start <branch_name> .
 ```
 
 
 The PATTS data files can be found in this directory:
 
-```platform/assets/speech_synthesis/patts```
+```src/platform/assets/speech_synthesis/patts```
 
 When updating the files, the native client files (nexe) need to be zipped.