Add Android NDK build for WebRTC

masters/master.client.webrtc/slaves.cfg

Index: masters/master.client.webrtc/slaves.cfg
diff --git a/masters/master.client.webrtc/slaves.cfg b/masters/master.client.webrtc/slaves.cfg
index 501618dbbbed79746d6280126f82de2c49c8989d..32a1097fbcf6fab7258308e24d7dd205c42c929b 100644
--- a/masters/master.client.webrtc/slaves.cfg
+++ b/masters/master.client.webrtc/slaves.cfg
@@ -3,7 +3,7 @@
 # found in the LICENSE file.
 
 slaves = [
-  # Linux
+  # Linux.
   {
     'master': 'WebRTC',
     'os': 'linux',
@@ -41,10 +41,11 @@ slaves = [
     'os': 'linux',
     'version': 'lucid',
     'bits': '64',
-    'builder': ['CrOS'],
+    'builder': ['CrOS', 'Android NDK'],
     'hostname': 'vm310-m3',
   },
-  # Mac
+
+  # Mac.
   {
     'master': 'WebRTC',
     'os': 'mac',
@@ -69,7 +70,8 @@ slaves = [
     'builder': ['MacAsan'],
     'hostname': 'vm674-m3',
   },
-  # Windows
+
+  # Windows.
   {
     'master': 'WebRTC',
     'os': 'win',