Add SK_IGNORE_TINY_FREETYPE_SIZE_FIX flag for Skia.

This is a temporary build flag to hold out a Skia change which will
affect very tiny text with FreeType. This will change the layout tree in
two layout tests on Linux and will cause them to better match the other
platforms. This flag will hold out the Skia change until these can be
rebaselined.

Bug: skia:8042
Change-Id: Iecb305343924dfc9f945352e94b81361a131bb22
Reviewed-on: https://chromium-review.googlesource.com/1099423Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Ben Wagner <bungeman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566954}

skia/BUILD.gn

@@ -119,9 +119,10 @@ config("skia_config") {
 
 # Internal-facing config for Skia library code.
 config("skia_library_config") {
+  defines = [ "SK_IGNORE_TINY_FREETYPE_SIZE_FIX" ]
+
   # These include directories are only included for Skia code and are not
   # exported to dependents.
-  defines = []
   include_dirs = [
     "//third_party/skia/include/codec",
     "//third_party/skia/include/private",