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"
 
-#import <AppKit/AppKit.h>
+#include <sstream>
+#include <string>
+#include <sys/utsname.h>
 
-#ifndef NSAppKitVersionNumber10_9
-#define NSAppKitVersionNumber10_9 1265
-#endif
+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
 
 namespace blink {
 
+bool IsOSLionOrEarlier()
+{
+    return MacOSXMinorVersion() <= LION_MINOR_VERSION;
+}
+
 bool IsOSMavericksOrEarlier()
 {
-    return floor(NSAppKitVersionNumber) <= NSAppKitVersionNumber10_9;
+    return MacOSXMinorVersion() <= MAVERICKS_MINOR_VERSION;
 }
 
 bool IsOSMavericks()
 {
-    return floor(NSAppKitVersionNumber) == NSAppKitVersionNumber10_9;
+    return MacOSXMinorVersion() == MAVERICKS_MINOR_VERSION;
 }
 
 } // namespace blink