doc: add quickstart to linux and macos

site/user/quick/macos.md

Index: site/user/quick/macos.md
diff --git a/site/user/quick/macos.md b/site/user/quick/macos.md
index ed74551d8b123fe118e2eb67d3e19d883775667b..c9d09a3bf101d34307d5bc80f3fe422cf6ef8e7b 100644
--- a/site/user/quick/macos.md
+++ b/site/user/quick/macos.md
@@ -1,6 +1,38 @@
 Mac OS X
 ========
 
+Quickstart
+----------
+
+1.  Install [XCode](http://developer.apple.com/xcode/).
+
+2.  Install depot tools.
+
+    <!--?prettify lang=sh?-->
+
+        git clone 'https://chromium.googlesource.com/chromium/tools/depot_tools.git'
+        export PATH="${PWD}/depot_tools:${PATH}"
+
+3.  Get Skia.
+
+    <!--?prettify lang=sh?-->
+
+        git clone 'https://skia.googlesource.com/skia'
+        cd skia
+
+4.  Build.
+
+    <!--?prettify lang=sh?-->
+
+        bin/sync-and-gyp && ninja -C out/Debug
+
+5.  Run DM (the Skia test app) and SampleApp.
+
+    <!--?prettify lang=sh?-->
+
+        out/Debug/dm
+        open out/Debug/SampleApp.app
+
 Prerequisites
 -------------