Restructure flushing relationship between GrContext, GrDrawingManager, and GrResourceCache.

Consolidates all flush actions into GrDrawingManager and makes GrContext::flush a passthrough.

Removes the unused and untested discard flush variation.

Replaces the indirect overbudget callback mechanism of GrResourceCache with a flag set by resource cache when it wants to flush that is checked after each draw by GrDrawContext.

Modifies GrResourceCache::notifyFlushOccurred() to take a param indicating whether it triggered the
flush that just occurred.

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Review-Url: https://codereview.chromium.org/2307053002
9 files changed