Fix memory leak in webrtc::MouseCursorMonitorMac

BUG=3815
R=sergeyu@chromium.org

Review URL: https://webrtc-codereview.appspot.com/24579004

Patch from Vicken Simonian <vsimon@gmail.com>.

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7187 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/desktop_capture/mouse_cursor_monitor_mac.mm

@@ -262,6 +262,7 @@ void MouseCursorMonitorMac::CaptureImage() {
       last_cursor_->hotspot().equals(hotspot) &&
       memcmp(last_cursor_->image()->data(), src_data,
              last_cursor_->image()->stride() * size.height()) == 0) {
+    CFRelease(image_data_ref);
     return;
   }