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

include/core/Sk64.h

Index: include/core/Sk64.h
diff --git a/include/core/Sk64.h b/include/core/Sk64.h
index 009744938fe397908ca544317f871eee568f8eac..c12a97c8a10ea7129137f33a41a9034578992a74 100644
--- a/include/core/Sk64.h
+++ b/include/core/Sk64.h
@@ -1,4 +1,3 @@
-
 /*
  * Copyright 2006 The Android Open Source Project
  *
@@ -6,7 +5,6 @@
  * found in the LICENSE file.
  */
 
-
 #ifndef Sk64_DEFINED
 #define Sk64_DEFINED
 
@@ -28,6 +26,11 @@ public:
     int64_t as64() const { return ((int64_t)fHi << 32) | fLo; }
     int64_t getLongLong() const { return this->as64(); }
 
+    void set64(int64_t value) {
+        fHi = (int32_t)(value >> 32);
+        fLo = (uint32_t)value;
+    }
+
     /** Returns non-zero if the Sk64 can be represented as a signed 32 bit integer
     */
     SkBool is32() const { return fHi == ((int32_t)fLo >> 31); }