Fix race condition in SkROBuffer.

tests/DataRefTest.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkData.h"
 #include "SkDataTable.h"
 #include "SkOSFile.h"
@@ skipping 276 matching lines @@
 DEF_TEST(RWBuffer, reporter) {
     // Knowing that the default capacity is 4096, choose N large enough so we force it to use
     // multiple buffers internally.
     const int N = 1000;
     SkROBuffer* readers[N];
     SkStream* streams[N];
 
     {
         SkRWBuffer buffer;
         for (int i = 0; i < N; ++i) {
-            if (0 == (i & 1)) {
-                buffer.append(gABC, 26);
-            } else {
-                memcpy(buffer.append(26), gABC, 26);
-            }
+            buffer.append(gABC, 26);
             readers[i] = buffer.newRBufferSnapshot();
             streams[i] = buffer.newStreamSnapshot();
         }
         REPORTER_ASSERT(reporter, N*26 == buffer.size());
     }
 
     for (int i = 0; i < N; ++i) {
         REPORTER_ASSERT(reporter, (i + 1) * 26U == readers[i]->size());
         check_alphabet_buffer(reporter, readers[i]);
         check_alphabet_stream(reporter, streams[i]);
@@ skipping 16 matching lines @@
     REPORTER_ASSERT(r, !iter.next());
     REPORTER_ASSERT(r, 0 == iter.size());
 }
 
 // Tests that it is safe to destruct an SkRWBuffer without appending
 // anything to it.
 DEF_TEST(RWBuffer_noAppend, r) {
     SkRWBuffer buffer;
     REPORTER_ASSERT(r, 0 == buffer.size());
 }