Always return the full remaining buffer capacity from makeSpaceAtLeast
Always return the full remaining buffer capacity from makeSpaceAtLeast

In the case where the blocks were empty we used to return the
fallbackSize as opposed to the actual size of the block.

Bug: skia:10419
Change-Id: Ie36c81f3b98bf8e95a2881356489ac54a842b787
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/304437
Commit-Queue: Chris Dalton <ef7fc3a08ada7d31f16e9a18b5f3c728256e041e@google.com>
Reviewed-by: Brian Salomon <61fabaaf0876044aeedfd8e351e485c028d69e7b@google.com>

google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia