mac: Explicitly redeclare methods only available on 10.7+.

When compiling against an OSX 10.7+ SDK, explicitly redeclare methods only
available from an OSX 10.7+ SDK. This suppresses the clang warning
-Wpartial-availability, which will be turned on in the future.

BUG=chromium:471823
R=jiayl@webrtc.org, mark@chromium.org

Review URL: https://webrtc-codereview.appspot.com/44359004

Cr-Commit-Position: refs/heads/master@{#9163}
diff --git a/webrtc/modules/desktop_capture/mac/desktop_configuration.mm b/webrtc/modules/desktop_capture/mac/desktop_configuration.mm
index 35fa65b..cb39cd5 100644
--- a/webrtc/modules/desktop_capture/mac/desktop_configuration.mm
+++ b/webrtc/modules/desktop_capture/mac/desktop_configuration.mm
@@ -17,14 +17,14 @@
 #include "webrtc/system_wrappers/interface/logging.h"
 
 #if !defined(MAC_OS_X_VERSION_10_7) || \
-    MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_7
+    MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_7
 
 @interface NSScreen (LionAPI)
 - (CGFloat)backingScaleFactor;
 - (NSRect)convertRectToBacking:(NSRect)aRect;
 @end
 
-#endif  // 10.7
+#endif  // MAC_OS_X_VERSION_10_7
 
 namespace webrtc {