SkPDF: device to use SkTCopyOnFirstWrite<SkPaint>
SkPDF: device to use SkTCopyOnFirstWrite<SkPaint>

Change-Id: I6490faf3b3f27c3f4b3dbd918260f85c12952d39
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/206205
Auto-Submit: Hal Canary <fd9641b23487c8ee78406c27513624c460600766@google.com>
Commit-Queue: Ben Wagner <53965154ffeecc4a10886eab9259e95965f2979a@google.com>
Reviewed-by: Ben Wagner <53965154ffeecc4a10886eab9259e95965f2979a@google.com>

HalCanary/skia-hc,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,rubenvb/skia,rubenvb/skia,HalCanary/skia-hc,google/skia,rubenvb/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,rubenvb/skia,rubenvb/skia,rubenvb/skia,rubenvb/skia,rubenvb/skia,HalCanary/skia-hc,rubenvb/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,HalCanary/skia-hc,HalCanary/skia-hc,google/skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,HalCanary/skia-hc,HalCanary/skia-hc,rubenvb/skia,google/skia,HalCanary/skia-hc,google/skia,google/skia