fix win compiler div/zero

tests/FlateTest.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 "SkFlate.h"
 #include "SkStream.h"
@@ skipping 71 matching lines @@
 
     // Check that the uncompressed data matches the source data.
     SkAutoDataUnref uncompressedData(uncompressed.copyToData());
     REPORTER_ASSERT(reporter, dataSize == uncompressedData->size());
     if (dataSize == uncompressedData->size()) {
         REPORTER_ASSERT(reporter, memcmp(testData->data(),
                                          uncompressedData->data(),
                                          dataSize) == 0);
     }
 
+    if (compressedSize < 1) { return; }
+
     double compressionRatio = static_cast<double>(dataSize) / compressedSize;
     // Assert that some compression took place.
     REPORTER_ASSERT(reporter, compressionRatio > 1.2);
 
     if (reporter->verbose()) {
         SkDebugf("Flate Test: \t input size: " SK_SIZE_T_SPECIFIER
                  "\tcompressed size: " SK_SIZE_T_SPECIFIER
                  "\tratio: %.4g\n",
                  dataSize, compressedSize, compressionRatio);
     }
 }
 
 DEF_TEST(Flate, reporter) {
 #ifdef SK_HAS_ZLIB
     REPORTER_ASSERT(reporter, SkFlate::HaveFlate());
 #endif
     if (SkFlate::HaveFlate()) {
         SkMemoryStream memStream;
         TestFlate(reporter, &memStream, 512);
         TestFlate(reporter, &memStream, 10240);
 
         SkZeroSizeMemStream fileStream;
         TestFlate(reporter, &fileStream, 512);
         TestFlate(reporter, &fileStream, 10240);
     }
 }