Revert of remove Sk64 from public API, and start to remove usage internally

include/core/SkMath.h

Index: include/core/SkMath.h
diff --git a/include/core/SkMath.h b/include/core/SkMath.h
index ba6223ed06e732101140de41c8675886a2470340..affcadaf2c76749829bdfaa9258f27d92545578d 100644
--- a/include/core/SkMath.h
+++ b/include/core/SkMath.h
@@ -34,32 +34,6 @@
 /** Return the integer square root of n, treated as a SkFixed (16.16)
  */
 #define SkSqrt32(n)         SkSqrtBits(n, 15)
-
-// 64bit -> 32bit utilities
-
-/**
- *  Return true iff the 64bit value can exactly be represented in signed 32bits
- */
-static inline bool sk_64_isS32(int64_t value) {
-    return (int32_t)value == value;
-}
-
-/**
- *  Return the 64bit argument as signed 32bits, asserting in debug that the arg
- *  exactly fits in signed 32bits. In the release build, no checks are preformed
- *  and the return value if the arg does not fit is undefined.
- */
-static inline int32_t sk_64_asS32(int64_t value) {
-    SkASSERT(sk_64_isS32(value));
-    return (int32_t)value;
-}
-
-// Handy util that can be passed two ints, and will automatically promote to
-// 64bits before the multiply, so the caller doesn't have to remember to cast
-// e.g. (int64_t)a * b;
-static inline int64_t sk_64_mul(int64_t a, int64_t b) {
-    return a * b;
-}
 
 ///////////////////////////////////////////////////////////////////////////////