[core] Set priorData from cache only if resource is useable

In cases when cached resource is useable, yet don't have an expiration
timestamp, we provided data to the requester from the cache and the same
data was returned once 304 response was received from the network.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/mbgl/sprite/sprite_loader.cpp b/src/mbgl/sprite/sprite_loader.cpp
index 56f7abd50b..60bab2bf6e 100644
--- a/src/mbgl/sprite/sprite_loader.cpp
+++ b/src/mbgl/sprite/sprite_loader.cpp
@@ -60,7 +60,8 @@ void SpriteLoader::load(const std::string& url, FileSource& fileSource) {
             emitSpriteLoadedIfComplete();
         } else {
             // Only trigger a sprite loaded event we got new data.
-            loader->json = res.data;
+            assert(loader->json != res.data);
+            loader->json = std::move(res.data);
             emitSpriteLoadedIfComplete();
         }
     });
@@ -74,7 +75,8 @@ void SpriteLoader::load(const std::string& url, FileSource& fileSource) {
             loader->image = std::make_shared<std::string>();
             emitSpriteLoadedIfComplete();
         } else {
-            loader->image = res.data;
+            assert(loader->image != res.data);
+            loader->image = std::move(res.data);
             emitSpriteLoadedIfComplete();
         }
     });