Add an implementation path option to json_schema_compiler

build/json_schema_bundle_compile.gypi

Index: build/json_schema_bundle_compile.gypi
diff --git a/build/json_schema_bundle_compile.gypi b/build/json_schema_bundle_compile.gypi
index 630e9c6ad2ec937b87d1e43c404a497b8aac88c7..39576adf6830db473e33122072be9ce3ccacee74 100644
--- a/build/json_schema_bundle_compile.gypi
+++ b/build/json_schema_bundle_compile.gypi
@@ -9,8 +9,11 @@
     #   cc_dir: path to generated files
     #   root_namespace: the C++ namespace that all generated files go under
     # Functions and namespaces can be excluded by setting "nocompile" to true.
+    # The default root path of API implementation sources is
+    # chrome/browser/extensions/api and can be overridden by setting "impl_dir".
     'api_gen_dir': '<(DEPTH)/tools/json_schema_compiler',
     'api_gen': '<(api_gen_dir)/compiler.py',
+    'impl_dir%': 'chrome/browser/extensions/api',
   },
   'actions': [
     {
@@ -43,6 +46,7 @@
         '--destdir=<(SHARED_INTERMEDIATE_DIR)',
         '--namespace=<(root_namespace)',
         '--generator=cpp-bundle',
+        '--impl-dir=<(impl_dir)',
         '<@(schema_files)',
         '<@(non_compiled_schema_files)',
       ],