tools/android/loading Reduce taskqueue access rate.

This CL increases the number of URLs per ClovisTask, making them longer
to process, and thus reducing the rate at which workers pull tasks from
the queue.

Review-Url: https://codereview.chromium.org/2059683002
Cr-Commit-Position: refs/heads/master@{#399178}

tools/android/loading/cloud/frontend/clovis_frontend.py

@@ -210,7 +210,9 @@ def SplitClovisTask(task):
     task.ActionParams()['traces'] = traces
 
   # Compute the split key.
-  split_params_for_action = {'trace': ('urls', 1), 'report': ('traces', 5)}
+  # Keep the tasks small, but large enough to avoid "rate exceeded" errors when
+  # pulling them from the TaskQueue.
+  split_params_for_action = {'trace': ('urls', 3), 'report': ('traces', 5)}
   (split_key, slice_size) = split_params_for_action.get(task.Action(),
                                                         (None, 0))
   if not split_key: