build: move libcc patches to electron repo (#14104)

In the GN build, libchromiumcontent is no longer a distinct library, but
merely a container for a set of scripts and patches. Maintaining those
patches in a separate repository is tedious and error-prone, so merge
them into the main repo.

Once this is merged and GN is the default way to build Electron, the
libchromiumcontent repository can be archived.

script/README.md

@@ -0,0 +1,36 @@
+## get-patch
+
+Use it to save commits from upstream repositories as patch files.
+
+### Examples
+
+1. Write commit contents in the patch format to stdout.
+```
+$ ./script/get-patch --repo src --commit 8e8216e5
+```
+
+2. Create a patch file with a default name if a specified directory.
+```
+$ ./script/get-patch --repo src --commit 8e8216e5 --output-dir patches
+```
+
+3. Create a patch file with a custom name in the current directory.
+```
+$ ./script/get-patch --repo src --commit 8e8216e5 --filename my.patch
+```
+
+4. Create a patch file with a custom name in a specified directory.
+```
+$ ./script/get-patch --repo src --commit 8e8216e5 --output-dir patches --filename my.patch
+```
+
+5. Create patch files with default names in a specified directory.
+```
+$ ./script/get-patch --repo src --output-dir patches --commit 8e8216e5 164c37e3
+```
+
+6. Create patch files with custom names in a specified directory.
+Note that number of filenames must match the number of commits.
+```
+$ ./script/get-patch --repo src --output-dir patches --commit 8e8216e5 164c37e3 --filename first.patch second.patch
+```