Simplify the consume before traversal heuristic.

Calling doConsumeBatchedInput() from doTraversals() can result
in redundant attempts to consume batched input.  Instead of making
this call directly, just schedule consume batched input at the
same time as traversals are scheduled.  This should have the same
overall effect.

Bug: 6375101
Change-Id: Ie5799e6a68fedbd1978cca6d03852d9a7f1b1f64