chore: add explanation to resource_file_conflict.patch (#15612)

* chore: add explanation to resource_file_conflict.patch

* Update resource_file_conflict.patch

patches/common/chromium/resource_file_conflict.patch

@@ -8,6 +8,50 @@ that chrome code hardcodes require that we generate resources at these
 paths, but GN throws errors if there are multiple targets that generate the
 same files.
 
+This is due to the hardcoded names here:
+https://chromium.googlesource.com/chromium/src/+/69.0.3497.106/ui/base/resource/resource_bundle.cc#780
+and here:
+https://chromium.googlesource.com/chromium/src/+/69.0.3497.106/ui/base/resource/resource_bundle_mac.mm#50
+
+This isn't needed on Mac because resource files are copied into the app bundle,
+and are built in `$root_out_dir/electron_repack` (while Chromium's resources
+target `$root_out_dir/repack`), but on Windows and Linux, the resource files go
+directly in `$root_out_dir`, and so they conflict.
+
+We don't actually ever generate Chromium's resource paks, but without this
+patch, GN refuses to generate the ninja files:
+
+   ERROR at //tools/grit/repack.gni:35:3: Duplicate output file.
+     action(_repack_target_name) {
+     ^----------------------------
+   Two or more targets generate the same output:
+     chrome_100_percent.pak
+
+   This is can often be fixed by changing one of the target names, or by
+   setting an output_name on one of them.
+
+   Collisions:
+     //chrome:packed_resources_100_percent
+     //electron:packed_resources_100_percent
+
+   See //tools/grit/repack.gni:35:3: Collision.
+     action(_repack_target_name) {
+     ^----------------------------
+
+
+Some alternatives to this patch:
+
+1. Refactor upstream in such a way that the "chrome" pak names were
+   configurable, for instance by adding a method to ResourceBundle::Delegate that
+   LoadChromeResources would check.
+2. Pass a Delegate that overrides `GetPathForResourcePack`, check for the
+   `chrome_{100,200}_percent.pak` filenames, and rewrite them to
+   `electron_{100,200}_percent.pak`.
+3. Initialize the resource bundle with DO_NOT_LOAD_COMMON_RESOURCES and load
+   the paks ourselves.
+
+None of these options seems like a substantial maintainability win over this patch to me (@nornagon).
+
 diff --git a/chrome/BUILD.gn b/chrome/BUILD.gn
 index a47af42a5a5afc1560f11ee0ccfa5fc177745caa..db8311121e755eb955ff05dee61a9706ae747977 100644
 --- a/chrome/BUILD.gn