Make Instance::WaitAny with one future const

Change-Id: I08d21f885b48e14cfaf02319b395f9ebba0d481d
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/206554
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
diff --git a/generator/templates/api_cpp.h b/generator/templates/api_cpp.h
index 49315cb..7f0b017 100644
--- a/generator/templates/api_cpp.h
+++ b/generator/templates/api_cpp.h
@@ -561,7 +561,7 @@
         {% endfor %}
 
         {% if CppType == "Instance" %}
-            inline WaitStatus WaitAny(Future f, uint64_t timeout);
+            inline WaitStatus WaitAny(Future f, uint64_t timeout) const;
         {% endif %}
 
       private:
@@ -927,7 +927,7 @@
     {% endfor %}
 
     {% if CppType == "Instance" %}
-        WaitStatus Instance::WaitAny(Future f, uint64_t timeout) {
+        WaitStatus Instance::WaitAny(Future f, uint64_t timeout) const {
             FutureWaitInfo waitInfo { f };
             return WaitAny(1, &waitInfo, timeout);
         }