Reland #1: Fix the mechanism by which Blink determines OSX version number.

Source/platform/mac/VersionUtilMacTest.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 <AppKit/AppKit.h>
+#include <gtest/gtest.h>
+
+#ifndef NSAppKitVersionNumber10_7
+#define NSAppKitVersionNumber10_7 1138
+#endif
+
+#ifndef NSAppKitVersionNumber10_9
+#define NSAppKitVersionNumber10_9 1265
+#endif
+
+#ifndef NSAppKitVersionNumber10_10
+#define NSAppKitVersionNumber10_10 1343
+#endif
+
+// This number was determined by writing a tiny Cocoa App on 10.10.4.
+#define NSAppKitVersionNumber10_10Max 1348
+
+// AppKit version is loosely correlated to OSX version. It's still useful as a
+// sanity check in unit tests, though we don't want to rely on it in production
+// code.
+TEST(VersionUtilMac, AppKitVersions)
+{
+    if (floor(NSAppKitVersionNumber) <= NSAppKitVersionNumber10_7) {
+        EXPECT_TRUE(blink::IsOSLionOrEarlier());
+        EXPECT_TRUE(blink::IsOSMavericksOrEarlier());
+        EXPECT_FALSE(blink::IsOSMavericks());
+        return;
+    }
+
+    if (floor(NSAppKitVersionNumber) < NSAppKitVersionNumber10_9) {
+        EXPECT_FALSE(blink::IsOSLionOrEarlier());
+        EXPECT_TRUE(blink::IsOSMavericksOrEarlier());
+        EXPECT_FALSE(blink::IsOSMavericks());
+        return;
+    }
+    if (floor(NSAppKitVersionNumber) == NSAppKitVersionNumber10_9) {
+        EXPECT_FALSE(blink::IsOSLionOrEarlier());
+        EXPECT_TRUE(blink::IsOSMavericksOrEarlier());
+        EXPECT_TRUE(blink::IsOSMavericks());
+        return;
+    }
+    if (floor(NSAppKitVersionNumber) <= NSAppKitVersionNumber10_10Max &&
+        floor(NSAppKitVersionNumber) >=  NSAppKitVersionNumber10_10) {
+        EXPECT_FALSE(blink::IsOSLionOrEarlier());
+        EXPECT_FALSE(blink::IsOSMavericksOrEarlier());
+        EXPECT_FALSE(blink::IsOSMavericks());
+        return;
+    }
+}