Only perform matrix concat when actually logging histograms Bug: skia: Change-Id: I61a710b570601d0d1178cf1dbe0d46d20872e9f1 Reviewed-on: https://skia-review.googlesource.com/c/193364 Commit-Queue: Michael Ludwig <michaelludwig@google.com> Reviewed-by: Brian Salomon <bsalomon@google.com>