'gasp' to control symmetric rendering on Windows.
'gasp' to control symmetric rendering on Windows.

Currently Skia tries hard to use symmetric rendering with DirectWrite
as often as possible. However, particularly on Windows 7 with CJK fonts,
thin horizontal strokes can be rendered without sufficient contrast
because the font was relying on the 6x1 oversampling for what is
effecitvely drop-out control. This change will only allow symmetric
rendering if the font allows it in the 'gasp' table.

BUG=chromium:645055

Change-Id: I45a9d5e4a0b49bb969c44fb20dc92528dfe9c48d
Reviewed-on: https://skia-review.googlesource.com/8268
Reviewed-by: Florin Malita <a8262bf13ea8c26821e91ea9bca6740a77c96dcd@chromium.org>
Commit-Queue: Ben Wagner <53965154ffeecc4a10886eab9259e95965f2979a@google.com>

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