Include used STL header files

Without these, cpplint's include-what-you-use fails.

Bug: None
Test: Build
Change-Id: I99954688b0041b10cfb7c18c8744cd889bf7a22e
diff --git a/service/gatt_server.h b/service/gatt_server.h
index 84ee165..e35b60a 100644
--- a/service/gatt_server.h
+++ b/service/gatt_server.h
@@ -19,6 +19,7 @@
 #include <deque>
 #include <functional>
 #include <mutex>
+#include <string>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>
diff --git a/service/hal/fake_bluetooth_gatt_interface.h b/service/hal/fake_bluetooth_gatt_interface.h
index c96f7f0..fc10434 100644
--- a/service/hal/fake_bluetooth_gatt_interface.h
+++ b/service/hal/fake_bluetooth_gatt_interface.h
@@ -16,6 +16,8 @@
 
 #pragma once
 
+#include <vector>
+
 #include <base/macros.h>
 #include <base/observer_list.h>