Add cast and assignment operators to SkAtomic.

include/core/SkAtomics.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkAtomics_DEFINED
 #define SkAtomics_DEFINED
 
@@ skipping 39 matching lines @@
 
     // It is essential we return by value rather than by const&.  fVal may change at any time.
     T load(sk_memory_order mo = sk_memory_order_seq_cst) const {
         return sk_atomic_load(&fVal, mo);
     }
 
     void store(const T& val, sk_memory_order mo = sk_memory_order_seq_cst) {
         sk_atomic_store(&fVal, val, mo);
     }
 
+    // Alias for .load(sk_memory_order_seq_cst).
+    operator T() const {
+        return this->load();
+    }
+
+    // Alias for .store(v, sk_memory_order_seq_cst).
+    T operator=(const T& v) {
+        this->store(v);
+        return v;
+    }
+
     T fetch_add(const T& val, sk_memory_order mo = sk_memory_order_seq_cst) {
         return sk_atomic_fetch_add(&fVal, val, mo);
     }
 
     T fetch_sub(const T& val, sk_memory_order mo = sk_memory_order_seq_cst) {
         return sk_atomic_fetch_sub(&fVal, val, mo);
     }
 
     bool compare_exchange(T* expected, const T& desired,
                           sk_memory_order success = sk_memory_order_seq_cst,
@@ skipping 46 matching lines @@
 template <typename T>
 T sk_acquire_load(T* ptr) { return sk_atomic_load(ptr, sk_memory_order_acquire); }
 
 template <typename T>
 void sk_release_store(T* ptr, T val) { sk_atomic_store(ptr, val, sk_memory_order_release); }
 
 inline void sk_membar_acquire__after_atomic_dec() {}
 inline void sk_membar_acquire__after_atomic_conditional_inc() {}
 
 #endif//SkAtomics_DEFINED