Add support for repeated keys in TaskRequest.

appengine/swarming/server/task_to_run.py

Index: appengine/swarming/server/task_to_run.py
diff --git a/appengine/swarming/server/task_to_run.py b/appengine/swarming/server/task_to_run.py
index de69703f6263203344cb2e10fd2f2586bb22a09d..d8c8bd14c6bd880ad9026b45dc73c74f1ffae940 100644
--- a/appengine/swarming/server/task_to_run.py
+++ b/appengine/swarming/server/task_to_run.py
@@ -427,17 +427,17 @@ def validate_to_run_key(task_key):
 
 
 def match_dimensions(request_dimensions, bot_dimensions):
-  """Returns True if the bot dimensions satisfies the request dimensions."""
-  assert isinstance(request_dimensions, dict), request_dimensions
+  """Returns True if the bot dimensions satisfies the request dimensions.
+
+  Arguments:
+    request_dimensions: list(tuple(unicode, unicode)).
+    bot_dimensions: dict(unicode: list(unicode)).
+  """
+  assert isinstance(request_dimensions, list), request_dimensions
   assert isinstance(bot_dimensions, dict), bot_dimensions
-  if frozenset(request_dimensions).difference(bot_dimensions):
-    return False
-  for key, required in request_dimensions.iteritems():
-    bot_value = bot_dimensions[key]
-    if isinstance(bot_value, (list, tuple)):
-      if required not in bot_value:
-        return False
-    elif required != bot_value:
+  for key, required in request_dimensions:
+    bot_value = bot_dimensions.get(key)
+    if not bot_value or required not in bot_value:
       return False
   return True