libgui: no use readString16Inplace

This uses readString16Inplace, which we may try to remove, in order to
make it possible libbinder can use utf-8 internally (and save space).

Bug: 172502290
Test: boot
Change-Id: I99761ebdcaa051363eabd9d577ca41b6d4d66880
diff --git a/libs/gui/view/Surface.cpp b/libs/gui/view/Surface.cpp
index d64dfd5..d98ffc6 100644
--- a/libs/gui/view/Surface.cpp
+++ b/libs/gui/view/Surface.cpp
@@ -72,13 +72,9 @@
 }
 
 String16 Surface::readMaybeEmptyString16(const Parcel* parcel) {
-    size_t len;
-    const char16_t* str = parcel->readString16Inplace(&len);
-    if (str != nullptr) {
-        return String16(str, len);
-    } else {
-        return String16();
-    }
+    std::optional<String16> str;
+    parcel->readString16(&str);
+    return str.value_or(String16());
 }
 
 } // namespace view