Revert of Fix the mechanism by which Blink determines OSX version number.

Source/platform/mac/VersionUtilMac.mm

 // Copyright 2015 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.
 
 #import "config.h"
 #import "platform/mac/VersionUtilMac.h"
 
-#include <sstream>
-#include <string>
-#include <sys/utsname.h>
+#import <AppKit/AppKit.h>
 
-namespace {
-
-// Returns the running system's Darwin major version. Don't call this, it's
-// an implementation detail and its result is meant to be cached by
-// MacOSXMinorVersion.
-int DarwinMajorVersionInternal()
-{
-    // The implementation of this method was copied from Chromium, with minor
-    // modifications to avoid the use of methods in base/. For further details,
-    // see
-    // https://code.google.com/p/chromium/codesearch#chromium/src/base/mac/mac_util.mm
-    struct utsname unameInfo;
-    if (uname(&unameInfo) != 0)
-        return 0;
-
-    if (strcmp(unameInfo.sysname, "Darwin") != 0)
-        return 0;
-
-    std::string releaseString(unameInfo.release);
-    size_t pos = releaseString.find_first_of('.');
-    if (pos == std::string::npos)
-        return 0;
-
-    std::istringstream convert(releaseString.substr(0, pos));
-    int majorVersion;
-    if (!(convert >> majorVersion))
-        return 0;
-
-    return majorVersion;
-}
-
-// Returns the running system's Mac OS X minor version. This is the |y| value
-// in 10.y or 10.y.z. Don't call this, it's an implementation detail and the
-// result is meant to be cached by MacOSXMinorVersion.
-int MacOSXMinorVersionInternal()
-{
-    int darwinMajorVersion = DarwinMajorVersionInternal();
-    return darwinMajorVersion - 4;
-}
-
-// Returns the running system's Mac OS X minor version. This is the |y| value
-// in 10.y or 10.y.z.
-int MacOSXMinorVersion()
-{
-    static int minorVersion = MacOSXMinorVersionInternal();
-    return minorVersion;
-}
-
-enum {
-    LION_MINOR_VERSION = 7,
-    MAVERICKS_MINOR_VERSION = 9,
-};
-
-} // namespace
+#ifndef NSAppKitVersionNumber10_9
+#define NSAppKitVersionNumber10_9 1265
+#endif
 
 namespace blink {
 
-bool IsOSLionOrEarlier()
-{
-    return MacOSXMinorVersion() <= LION_MINOR_VERSION;
-}
-
 bool IsOSMavericksOrEarlier()
 {
-    return MacOSXMinorVersion() <= MAVERICKS_MINOR_VERSION;
+    return floor(NSAppKitVersionNumber) <= NSAppKitVersionNumber10_9;
 }
 
 bool IsOSMavericks()
 {
-    return MacOSXMinorVersion() == MAVERICKS_MINOR_VERSION;
+    return floor(NSAppKitVersionNumber) == NSAppKitVersionNumber10_9;
 }
 
 } // namespace blink