Pure pedantry: Replace all ".size() == 0" with ".empty()".

ui/gfx/codec/jpeg_codec_unittest.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <math.h>
 
 #include "base/basictypes.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/gfx/codec/jpeg_codec.h"
 
@@ skipping 58 matching lines @@
 static double jpeg_equality_threshold = 1.0;
 
 // Computes the average difference between each value in a and b. A and b
 // should be the same size. Used to see if two images are approximately equal
 // in the presence of compression.
 static double AveragePixelDelta(const std::vector<unsigned char>& a,
                                 const std::vector<unsigned char>& b) {
   // if the sizes are different, say the average difference is the maximum
   if (a.size() != b.size())
     return 255.0;
-  if (a.size() == 0)
+  if (a.empty())
     return 0;  // prevent divide by 0 below
 
   double acc = 0.0;
   for (size_t i = 0; i < a.size(); i++)
     acc += fabs(static_cast<double>(a[i]) - static_cast<double>(b[i]));
 
   return acc / static_cast<double>(a.size());
 }
 
 static void MakeRGBImage(int w, int h, std::vector<unsigned char>* dat) {
@@ skipping 118 matching lines @@
                     JPEGCodec::FORMAT_RGB, &output,
                     &outw, &outh);
 
   JPEGCodec::Decode(kTopSitesMigrationTestImage,
                     arraysize(kTopSitesMigrationTestImage),
                     JPEGCodec::FORMAT_RGBA, &output,
                     &outw, &outh);
 }
 
 }  // namespace gfx