Flush less frequently in QueryGL. StandardQueryGL flushes with every pause/resume/end operation to make sure the list of pending queries does not grow too large. This ended up trying to flush the queries as soon as they were ended and unlikely to have results ready. Add a threshold of pending queries before flushing, hopefully delaying the flush calls until the queries are ready. This is a speculative fix for a GPU hang in query flushing. Bug: chromium:1078754 Change-Id: I38300995ee6576dee8c8c26fa9ccad26e269337a Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2401178 Reviewed-by: Jonah Ryan-Davis <jonahr@google.com> Commit-Queue: Geoff Lang <geofflang@chromium.org>