Add quickstart instructions for UI

Change-Id: If0b54370f03a853f7fe16498448fd27a7b62ae57
diff --git a/docs/build-instructions.md b/docs/build-instructions.md
index 823f05b..9ba085c 100644
--- a/docs/build-instructions.md
+++ b/docs/build-instructions.md
@@ -24,7 +24,7 @@
 **Standalone checkout**:  
 All dependent libraries are self-hosted and pulled through:
 ```
-$ tools/install-build-deps [--no-android]
+$ tools/install-build-deps [--no-android] [--ui]
 ```
 
 **Android tree**:  
@@ -51,6 +51,12 @@
 $ tools/ninja -C out/android
 ```
 
+To build the UI (remember to run `tools/install-build-deps --ui` first):
+
+```
+$ tools/ninja -C out/android ui
+```
+
 **Android tree**:  
 `$ mmma external/perfetto`
 or