Generate all extension schema namespaces as "api" and instead vary the generated bundle names.

build/json_schema_api.gni

Index: build/json_schema_api.gni
diff --git a/build/json_schema_api.gni b/build/json_schema_api.gni
index e1c2d33409d52ad4d92f6e233e3ce31f84789574..479897a6999fb33cfbb7a9ca56a9bfc6674e6486 100644
--- a/build/json_schema_api.gni
+++ b/build/json_schema_api.gni
@@ -16,6 +16,11 @@
 #     namespace for each API. Use %(namespace)s to replace with the API
 #     namespace, like "toplevel::%(namespace)s_api".
 #
+# bundle_name [optional]:
+#     A string to prepend to generated bundle class names, so that multiple
+#     bundle rules can be used without conflicting.  Only used with one of
+#     the cpp-bundle generators.
+#
 # schema_include_rules [optional]
 #     A list of paths to include when searching for referenced objects,
 #     with the namespace separated by a :.
@@ -63,6 +68,11 @@ template("json_schema_api") {
   bundle_registration =
       defined(invoker.bundle_registration) && invoker.bundle_registration
 
+  bundle_name = ""
+  if (defined(invoker.bundle_name)) {
+    bundle_name = invoker.bundle_name
+  }
+
   schema_include_rules = ""
   if (defined(invoker.schema_include_rules)) {
     schema_include_rules = invoker.schema_include_rules
@@ -86,6 +96,7 @@ template("json_schema_api") {
     "$compiler_root/cc_generator.py",
     "$compiler_root/code.py",
     "$compiler_root/compiler.py",
+    "$compiler_root/cpp_bundle_generator.py",
     "$compiler_root/cpp_generator.py",
     "$compiler_root/cpp_type_generator.py",
     "$compiler_root/cpp_util.py",
@@ -139,6 +150,7 @@ template("json_schema_api") {
                "--root=" + rebase_path("//", root_build_dir),
                "--destdir=" + rebase_path(root_gen_dir, root_build_dir),
                "--namespace=$root_namespace",
+               "--bundle-name=$bundle_name",
                "--generator=cpp-bundle-schema",
                "--include-rules=$schema_include_rules",
              ] + rebase_path(invoker.sources, root_build_dir) +
@@ -171,6 +183,7 @@ template("json_schema_api") {
                "--root=" + rebase_path("//", root_build_dir),
                "--destdir=" + rebase_path(root_gen_dir, root_build_dir),
                "--namespace=$root_namespace",
+               "--bundle-name=$bundle_name",
                "--generator=cpp-bundle-registration",
                "--impl-dir=$gen_child_dir",
                "--include-rules=$schema_include_rules",