remove cruft from SkTypes.h, including SkBool

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1548223002

TBR=

Review URL: https://codereview.chromium.org/1548223002
diff --git a/include/utils/SkInterpolator.h b/include/utils/SkInterpolator.h
index 18203d0..9547cec 100644
--- a/include/utils/SkInterpolator.h
+++ b/include/utils/SkInterpolator.h
@@ -59,7 +59,7 @@
         fFlags = SkToU8((fFlags & ~kReset) | (int)reset);
     }
 
-    Result  timeToT(SkMSec time, SkScalar* T, int* index, SkBool* exact) const;
+    Result  timeToT(SkMSec time, SkScalar* T, int* index, bool* exact) const;
 
 protected:
     enum Flags {