Move extension API schema registration to ExtensionsClient.

apps/shell/common/shell_extensions_client.cc

Index: apps/shell/common/shell_extensions_client.cc
diff --git a/apps/shell/common/shell_extensions_client.cc b/apps/shell/common/shell_extensions_client.cc
index 2dac9e121f96f5f3cf03e46c44e5803237573389..cc2f055762b6cd7c08ecf3489361376bae8f035b 100644
--- a/apps/shell/common/shell_extensions_client.cc
+++ b/apps/shell/common/shell_extensions_client.cc
@@ -207,6 +207,10 @@ base::StringPiece ShellExtensionsClient::GetAPISchema(
   return extensions::core_api::GeneratedSchemas::Get(name);
 }
 
+void ShellExtensionsClient::RegisterAPISchemaResources(
+    extensions::ExtensionAPI* api) const {
+}
+
 bool ShellExtensionsClient::ShouldSuppressFatalErrors() const { return true; }
 
 }  // namespace apps