SkScalerContext::getImage less brittle.
SkScalerContext::getImage less brittle.

Properly handle edge cases like
 * the temporary glyph being a different size than expected
 * filters which reduce in size
 * filters which return false to indicate no filtering has been done

Bug: chromium:1190525
Change-Id: Ibc53eb1d7014210019e96cd6bae3e256d967be54
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/392156
Commit-Queue: Ben Wagner <53965154ffeecc4a10886eab9259e95965f2979a@google.com>
Reviewed-by: Herb Derby <9e12a3d2bbf73546e47cc9958f6ba8f3215b7eaf@google.com>

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