WebRTC: Update to new machines after a->b lab move.

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 3973a606416c5c8b598f164f289afd7519d932c0..aece3c708a1d209f8ecf6bac93c6191cf1979bac 100644
--- a/masters/master.client.webrtc/slaves.cfg
+++ b/masters/master.client.webrtc/slaves.cfg
@@ -78,7 +78,7 @@ slaves = [
     'builder': [
       'Android32 Tests (L Nexus5)',
     ],
-    'hostname': 'build1-a3',
+    'hostname': 'build18-b3',
   },
   {
     'master': 'WebRTC',
@@ -88,7 +88,7 @@ slaves = [
     'builder': [
       'Android32 Tests (L Nexus5)(dbg)',
     ],
-    'hostname': 'build2-a3',
+    'hostname': 'build19-b3',
   },
 ] + [
   {
@@ -99,7 +99,7 @@ slaves = [
     'builder': [
       'Android32 Tests (L Nexus7.2)',
     ],
-    'hostname': 'build7-a3',
+    'hostname': 'build22-b3',
   },
   {
     'master': 'WebRTC',
@@ -109,7 +109,7 @@ slaves = [
     'builder': [
       'Android32 Tests (L Nexus7.2)(dbg)',
     ],
-    'hostname': 'build8-a3',
+    'hostname': 'build21-b3',
   },
   {
     'master': 'WebRTC',
@@ -119,7 +119,7 @@ slaves = [
     'builder': [
       'Android64 Tests (L Nexus9)',
     ],
-    'hostname': 'build34-a3',
+    'hostname': 'build17-b3',
   },
 ] + [
   # Mac.
@@ -211,6 +211,6 @@ slaves = [
     'builder': [
       'Win32 Release [large tests]',
     ],
-    'hostname': 'chromeperf90',
+    'hostname': 'build20-b3',
   }
 ]