[Math builtins]: Cleanup in ieee754, restoring MSUN version of log2().

test/unittests/base/ieee754-unittest.cc

 // Copyright 2016 the V8 project 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 <limits>
 
 #include "src/base/ieee754.h"
 #include "src/base/macros.h"
 #include "testing/gmock-support.h"
 #include "testing/gtest-support.h"
@@ skipping 149 matching lines @@
   EXPECT_THAT(log10(-1.0), IsNaN());
   EXPECT_EQ(-std::numeric_limits<double>::infinity(), log10(0.0));
   EXPECT_EQ(-std::numeric_limits<double>::infinity(), log10(-0.0));
   EXPECT_EQ(std::numeric_limits<double>::infinity(),
             log10(std::numeric_limits<double>::infinity()));
   EXPECT_EQ(3.0, log10(1000.0));
   EXPECT_EQ(14.0, log10(100000000000000));  // log10(10 ^ 14)
   EXPECT_EQ(3.7389561269540406, log10(5482.2158));
   EXPECT_EQ(14.661551142893833, log10(458723662312872.125782332587));
   EXPECT_EQ(-0.9083828622192334, log10(0.12348583358871));
+  EXPECT_EQ(5.0, log10(100000.0));
 }
 
 TEST(Ieee754, cbrt) {
   EXPECT_THAT(cbrt(std::numeric_limits<double>::quiet_NaN()), IsNaN());
   EXPECT_THAT(cbrt(std::numeric_limits<double>::signaling_NaN()), IsNaN());
   EXPECT_EQ(std::numeric_limits<double>::infinity(),
             cbrt(std::numeric_limits<double>::infinity()));
   EXPECT_EQ(-std::numeric_limits<double>::infinity(),
             cbrt(-std::numeric_limits<double>::infinity()));
   EXPECT_EQ(1.4422495703074083, cbrt(3));
   EXPECT_EQ(100, cbrt(100 * 100 * 100));
   EXPECT_EQ(46.415888336127786, cbrt(100000));
 }
 
 }  // namespace ieee754
 }  // namespace base
 }  // namespace v8