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There exists lots of tracing for the old CAOpenGLLayer path in
ui::IOSurfaceLayerHelper. The new path doesn't have this tracing.

This adds tracing for the swap state (this is the pseudo-thread
counter corresponding to PendingSwapAck in ui::IOSurfaceLayerHelper,
along with trace events for the important functions related to swaps
on Mac.

BUG=487882

Review URL: https://codereview.chromium.org/1137093003

Cr-Commit-Position: refs/heads/master@{#329878}