Make some file_system_provider_capabilities fields optional.

chrome/common/extensions/api/file_system_provider_capabilities/file_system_provider_capabilities_handler.cc

Index: chrome/common/extensions/api/file_system_provider_capabilities/file_system_provider_capabilities_handler.cc
diff --git a/chrome/common/extensions/api/file_system_provider_capabilities/file_system_provider_capabilities_handler.cc b/chrome/common/extensions/api/file_system_provider_capabilities/file_system_provider_capabilities_handler.cc
index c3dc906cea8e0dc5f00180483399ce2297e23063..d959ad725e863d39f24e72df7cd3f8f5f3907da3 100644
--- a/chrome/common/extensions/api/file_system_provider_capabilities/file_system_provider_capabilities_handler.cc
+++ b/chrome/common/extensions/api/file_system_provider_capabilities/file_system_provider_capabilities_handler.cc
@@ -95,9 +95,14 @@ bool FileSystemProviderCapabilitiesHandler::Parse(Extension* extension,
   }
 
   scoped_ptr<FileSystemProviderCapabilities> capabilities(
-      new FileSystemProviderCapabilities(idl_capabilities.configurable,
-                                         idl_capabilities.multiple_mounts,
-                                         source));
+      new FileSystemProviderCapabilities(
+          idl_capabilities.configurable.get()
+              ? *idl_capabilities.configurable.get()
+              : false /* false by default */,
+          idl_capabilities.multiple_mounts.get()
+              ? *idl_capabilities.multiple_mounts.get()
+              : false /* false by default */,
+          source));
 
   extension->SetManifestData(manifest_keys::kFileSystemProviderCapabilities,
                              capabilities.release());