Add tests for STArray swap

include/core/SkTArray.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkTArray_DEFINED
 #define SkTArray_DEFINED
 
@@ skipping 255 matching lines @@
         if (newCount > fCount) {
             this->push_back_n(newCount - fCount);
         } else if (newCount < fCount) {
             this->pop_back_n(fCount - newCount);
         }
     }
 
     /** Swaps the contents of this array with that array. Does a pointer swap if possible,
         otherwise copies the T values. */
     void swap(SkTArray* that) {
+        if (this == that) {
+            return;
+        }
         if (this->fPreAllocMemArray != this->fItemArray &&
             that->fPreAllocMemArray != that->fItemArray) {
             // If neither is using a preallocated array then just swap.
             SkTSwap(fItemArray, that->fItemArray);
             SkTSwap(fCount, that->fCount);
             SkTSwap(fAllocCount, that->fAllocCount);
         } else {
             // This could be more optimal...
             SkTArray copy(*that);
             *that = *this;
@@ skipping 251 matching lines @@
     SkSTArray& operator= (const INHERITED& array) {
         INHERITED::operator=(array);
         return *this;
     }
 
 private:
     SkAlignedSTStorage<N,T> fStorage;
 };
 
 #endif