Convert most Chromium presubmit files to use new multiple-tryserver-compatible protocol

base/PRESUBMIT.py

Index: base/PRESUBMIT.py
diff --git a/base/PRESUBMIT.py b/base/PRESUBMIT.py
index 7137c5a0101e42eb797787ef6d4e26abc38be1ce..8082590f88fdd5c8f40afaf04401e2ef39b8f764 100644
--- a/base/PRESUBMIT.py
+++ b/base/PRESUBMIT.py
@@ -48,9 +48,11 @@ def CheckChangeOnCommit(input_api, output_api):
   return results
 
 
-def GetPreferredTrySlaves():
-  return [
-    'linux_rel:sync_integration_tests',
-    'mac_rel:sync_integration_tests',
-    'win_rel:sync_integration_tests',
-  ]
+def GetPreferredTryMasters(project, change):
+  return {
+    'tryserver.chromium': {
+      'linux_rel': set(['sync_integration_tests']),
+      'mac_rel': set(['sync_integration_tests']),
+      'win_rel': set(['sync_integration_tests']),
+    }
+  }