add missing include

tests/ChecksumTest.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
+#include "SkChecksum.h"
 #include "SkOpts.h"
 #include "SkRandom.h"
 #include "Test.h"
 
 DEF_TEST(Checksum, r) {
     // Put 128 random bytes into two identical buffers.  Any multiple of 4 will do.
     const size_t kBytes = SkAlign4(128);
     SkRandom rand;
     uint32_t data[kBytes/4], tweaked[kBytes/4];
     for (size_t i = 0; i < SK_ARRAY_COUNT(tweaked); ++i) {
@@ skipping 16 matching lines @@
         REPORTER_ASSERT(r, tweakedHash == SkOpts::hash(tweaked, kBytes));
         tweaked[j] = saved;
     }
 }
 
 DEF_TEST(GoodHash, r) {
     // 4 bytes --> hits SkChecksum::Mix fast path.
     REPORTER_ASSERT(r, SkGoodHash()(( int32_t)4) ==  614249093);
     REPORTER_ASSERT(r, SkGoodHash()((uint32_t)4) ==  614249093);
 }