Fix a crash when built with 10.7 SDK running on OS X 10.6

content/browser/renderer_host/render_widget_host_view_mac.mm

Index: content/browser/renderer_host/render_widget_host_view_mac.mm
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index 0a1aeaf2aa980020c38d4793ccf9183aac977091..758dab5234d4ef19014f69bac2da77d7b8c5e584 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -2378,11 +2378,18 @@ void RenderWidgetHostViewMac::FrameSwapped() {
 
   NSNotificationCenter* notificationCenter =
       [NSNotificationCenter defaultCenter];
+
+  // Backing property notifications crash on 10.6 when building with the 10.7
+  // SDK, see http://crbug.com/260595.
+  BOOL supportsBackingPropertiesNotification = base::mac::IsOSLionOrLater();
+
   if (oldWindow) {
-    [notificationCenter
-        removeObserver:self
-                  name:NSWindowDidChangeBackingPropertiesNotification
-                object:oldWindow];
+    if (supportsBackingPropertiesNotification) {
+      [notificationCenter
+          removeObserver:self
+                    name:NSWindowDidChangeBackingPropertiesNotification
+                  object:oldWindow];
+    }
     [notificationCenter
         removeObserver:self
                   name:NSWindowDidMoveNotification
@@ -2393,11 +2400,13 @@ void RenderWidgetHostViewMac::FrameSwapped() {
                 object:oldWindow];
   }
   if (newWindow) {
-    [notificationCenter
-        addObserver:self
-           selector:@selector(windowDidChangeBackingProperties:)
-               name:NSWindowDidChangeBackingPropertiesNotification
-             object:newWindow];
+    if (supportsBackingPropertiesNotification) {
+      [notificationCenter
+          addObserver:self
+             selector:@selector(windowDidChangeBackingProperties:)
+                 name:NSWindowDidChangeBackingPropertiesNotification
+               object:newWindow];
+    }
     [notificationCenter
         addObserver:self
            selector:@selector(windowChangedGlobalFrame:)