Remove SkImageInfoIsGammaCorrect, etc...

Our internal definition is (and will continue to be) that anything with
a color space is gamma correct. F16 is irrelevant (whether or not we
choose to support untagged F16). This makes these helpers less than
helpful, and lets us remove them from (public) API.

API change is just removal (of unused functions).

TBR=reed@google.com

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4228

Change-Id: Ia84a423548bfee14a3ba4a43d6d5b8c4686fb5ff
Reviewed-on: https://skia-review.googlesource.com/4228
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
diff --git a/dm/DM.cpp b/dm/DM.cpp
index 71d3150..150b994 100644
--- a/dm/DM.cpp
+++ b/dm/DM.cpp
@@ -1143,7 +1143,7 @@
                             const SkBitmap* bitmap) {
         bool gammaCorrect = false;
         if (bitmap) {
-            gammaCorrect = SkImageInfoIsGammaCorrect(bitmap->info());
+            gammaCorrect = SkToBool(bitmap->info().colorSpace());
         }
 
         JsonWriter::BitmapResult result;