Index: render_widget_host_view_mac.mm
===================================================================
--- render_widget_host_view_mac.mm	(revision 202711)
+++ render_widget_host_view_mac.mm	(working copy)
@@ -4,6 +4,7 @@
 
 #include "content/browser/renderer_host/render_widget_host_view_mac.h"
 
+#import <objc/runtime.h>
 #include <QuartzCore/QuartzCore.h>
 
 #include "base/bind.h"
@@ -125,6 +126,29 @@
   return modifiers;
 }
 
+// This method will return YES for OS X versions 10.7.3 and later, and NO
+// otherwise.
+// Used to prevent a crash when building with the 10.7 SDK and accessing the
+// notification below. See: http://crbug.com/260595.
+static BOOL SupportsBackingPropertiesChangedNotification() {
+  // windowDidChangeBackingProperties: method has been added to the
+  // NSWindowDelegate protocol in 10.7.3, at the same time as the
+  // NSWindowDidChangeBackingPropertiesNotification notification was added.
+  // If the protocol contains this method description, the notification should
+  // be supported as well.
+  Protocol* windowDelegateProtocol = NSProtocolFromString(@"NSWindowDelegate");
+  struct objc_method_description methodDescription =
+      protocol_getMethodDescription(
+          windowDelegateProtocol,
+          @selector(windowDidChangeBackingProperties:),
+          NO,
+          YES);
+
+  // If the protocol does not contain the method, the returned method
+  // description is {NULL, NULL}
+  return methodDescription.name != NULL || methodDescription.types != NULL;
+}
+
 static float ScaleFactor(NSView* view) {
   return ui::GetScaleFactorScale(ui::GetScaleFactorForNativeView(view));
 }
@@ -1424,7 +1448,7 @@
     // Forget IOSurface since we are drawing a software frame now.
     if (compositing_iosurface_.get() &&
         compositing_iosurface_->HasIOSurface()) {
-      compositing_iosurface_->UnrefIOSurface();
+      compositing_iosurface_->ClearDrawable();
     }
   }
 }
@@ -2097,13 +2121,21 @@
 
   NSNotificationCenter* notificationCenter =
       [NSNotificationCenter defaultCenter];
+
+  // Backing property notifications crash on 10.6 when building with the 10.7
+  // SDK, see http://crbug.com/260595.
+  static BOOL supportsBackingPropertiesNotification =
+      SupportsBackingPropertiesChangedNotification();
+
   if (oldWindow) {
+    if (supportsBackingPropertiesNotification) {
+      [notificationCenter
+          removeObserver:self
+                    name:NSWindowDidChangeBackingPropertiesNotification
+                  object:oldWindow];
+    }
     [notificationCenter
         removeObserver:self
-                  name:NSWindowDidChangeBackingPropertiesNotification
-                object:oldWindow];
-    [notificationCenter
-        removeObserver:self
                   name:NSWindowDidMoveNotification
                 object:oldWindow];
     [notificationCenter
@@ -2112,13 +2144,15 @@
                 object:oldWindow];
   }
   if (newWindow) {
+    if (supportsBackingPropertiesNotification) {
+      [notificationCenter
+          addObserver:self
+             selector:@selector(windowDidChangeBackingProperties:)
+                 name:NSWindowDidChangeBackingPropertiesNotification
+               object:newWindow];
+    }
     [notificationCenter
         addObserver:self
-           selector:@selector(windowDidChangeBackingProperties:)
-               name:NSWindowDidChangeBackingPropertiesNotification
-             object:newWindow];
-    [notificationCenter
-        addObserver:self
            selector:@selector(windowChangedGlobalFrame:)
                name:NSWindowDidMoveNotification
              object:newWindow];