Remove sk_64_isS32 and sk_64_asS32

This is an API change. I assume that only Skia uses these routines.

Change-Id: Iefc98fa5c0b83eb4f52c478e345fd99121ecb254
Reviewed-on: https://skia-review.googlesource.com/129440
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
diff --git a/src/codec/SkWebpCodec.cpp b/src/codec/SkWebpCodec.cpp
index 95ae9b9..757cde5 100644
--- a/src/codec/SkWebpCodec.cpp
+++ b/src/codec/SkWebpCodec.cpp
@@ -81,7 +81,7 @@
     {
         const int64_t size = sk_64_mul(width, height);
         // now check that if we are 4-bytes per pixel, we also don't overflow
-        if (!sk_64_isS32(size) || sk_64_asS32(size) > (0x7FFFFFFF >> 2)) {
+        if (!SkTFitsIn<int32_t>(size) || SkTo<int32_t>(size) > (0x7FFFFFFF >> 2)) {
             *result = kInvalidInput;
             return nullptr;
         }