Use C++17 structured binding in more places.

Bug: dawn:824
Change-Id: Ie39d4f622bfb3dcc3a74b03d594efcea7139a9dc
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/75069
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Loko Kung <lokokung@google.com>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/common/ConcurrentCache.h b/src/common/ConcurrentCache.h
index 0e93ddd..a1cab8d 100644
--- a/src/common/ConcurrentCache.h
+++ b/src/common/ConcurrentCache.h
@@ -37,8 +37,8 @@
 
     std::pair<T*, bool> Insert(T* object) {
         std::lock_guard<std::mutex> lock(mMutex);
-        auto insertion = mCache.insert(object);
-        return std::make_pair(*(insertion.first), insertion.second);
+        auto [value, inserted] = mCache.insert(object);
+        return {*value, inserted};
     }
 
     size_t Erase(T* object) {