Check that the upper bits are correct in the SkArenaAlloc footer.
Check that the upper bits are correct in the SkArenaAlloc footer.

TBR=mtklein@google.com

Change-Id: I8dc21778d1b8b24dd9d7b6919bb7e2bcfe090e82
Reviewed-on: https://skia-review.googlesource.com/7588
Commit-Queue: Herb Derby <9e12a3d2bbf73546e47cc9958f6ba8f3215b7eaf@google.com>
Reviewed-by: Herb Derby <9e12a3d2bbf73546e47cc9958f6ba8f3215b7eaf@google.com>

aosp-mirror/platform_external_skia,google/skia,google/skia,HalCanary/skia-hc,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,rubenvb/skia,HalCanary/skia-hc,google/skia,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,aosp-mirror/platform_external_skia,google/skia,rubenvb/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,rubenvb/skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,google/skia,HalCanary/skia-hc,HalCanary/skia-hc,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,HalCanary/skia-hc,rubenvb/skia,rubenvb/skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,rubenvb/skia,HalCanary/skia-hc,Hikari-no-Tenshi/android_external_skia,HalCanary/skia-hc,rubenvb/skia,Hikari-no-Tenshi/android_external_skia,google/skia,Hikari-no-Tenshi/android_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia