There may be instances where CEF requires changes to the source code for Chromium, Blink or third-party projects that are either not desired by those projects or that have not yet been merged into the source code versions of those projects used by CEF. To address this situation the CEF project adds a patch capability as part of cef_create_projects[.bat|sh] build step. This patch capability works as follows: 1. The CEF developer creates one or more patch files containing all required code changes and places those patch files in the "patches" subdirectory. 2. The CEF developer adds an entry for each patch file in the "patch.cfg" file. 3. When building CEF from source code the patch files are applied by the patcher.py tool via the cef_create_projects[.bat|sh] build step 4. When updating Chromium the patch_updater.py tool is used to update all patch files. See https://bitbucket.org/chromiumembedded/cef/wiki/ChromiumUpdate.md for more information about the update process.