Enable ClangTidy check performance-unnecessary-copy-initialization.

https://clang.llvm.org/extra/clang-tidy/checks/performance-unnecessary-copy-initialization.html

Finds local variable declarations that are initialized using the copy
constructor of a non-trivially-copyable type but it would suffice to
obtain a const reference.

The check is only applied if it is safe to replace the copy by a const
reference. This is the case when the variable is const qualified or when
it is only used as a const, i.e. only const methods or operators are
invoked on it, or it is used as const reference or value argument in
constructors or function calls.

Change-Id: I1261410deccd8ea64e85edec53fbd5360940e587
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/308759
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
diff --git a/tools/DDLPromiseImageHelper.cpp b/tools/DDLPromiseImageHelper.cpp
index 0ae1df7..35e8ed8 100644
--- a/tools/DDLPromiseImageHelper.cpp
+++ b/tools/DDLPromiseImageHelper.cpp
@@ -413,7 +413,7 @@
         }
 #endif
     } else {
-        GrBackendFormat backendFormat = curImage.backendFormat(0);
+        const GrBackendFormat& backendFormat = curImage.backendFormat(0);
         SkASSERT(backendFormat.isValid());
 
         // Each DDL recorder gets its own ref on the promise callback context for the