Access child storage over RPC. (#2586)

* Access child storage over RPC.

* Address review grumbles.

* Test happy case in child_storage rpc.

* Remove stray printlns

* Fix line widths.

* Bump runtime again.

* Fix genesis storage root calculation for light clients.

* Don't pass values to full_storage_root child_delta.

substrate/core/test-client/src/lib.rs

@@ -34,7 +34,8 @@ pub use keyring::{sr25519::Keyring as AuthorityKeyring, AccountKeyring};
 use std::{sync::Arc, collections::HashMap};
 use futures::future::FutureResult;
 use primitives::Blake2Hasher;
-use runtime_primitives::StorageOverlay;
+use primitives::storage::well_known_keys;
+use runtime_primitives::{StorageOverlay, ChildrenStorageOverlay};
 use runtime_primitives::traits::{
 	Block as BlockT, Header as HeaderT, Hash as HashT, NumberFor
 };
@@ -271,7 +272,7 @@ fn genesis_config(support_changes_trie: bool) -> GenesisConfig {
 fn genesis_storage(
 	support_changes_trie: bool,
 	extension: HashMap<Vec<u8>, Vec<u8>>
-) -> StorageOverlay {
+) -> (StorageOverlay, ChildrenStorageOverlay) {
 	let mut storage = genesis_config(support_changes_trie).genesis_map();
 	storage.extend(extension.into_iter());
 
@@ -280,7 +281,14 @@ fn genesis_storage(
 	);
 	let block: runtime::Block = client::genesis::construct_genesis_block(state_root);
 	storage.extend(additional_storage_with_genesis(&block));
-	storage
+
+	let mut child_storage = ChildrenStorageOverlay::default();
+	child_storage.insert(
+		well_known_keys::CHILD_STORAGE_KEY_PREFIX.iter().chain(b"test").cloned().collect(),
+		vec![(b"key".to_vec(), vec![42_u8])].into_iter().collect()
+	);
+
+	(storage, child_storage)
 }
 
 impl<Block: BlockT> client::light::fetcher::Fetcher<Block> for LightFetcher {