Destroy frontend and backend for Textures

Same idea as for buffers, Destroy can be used to free GPU memory
associated with resources without waiting for javascript garbage
collection to occur.

Bug: dawn:46
Change-Id: Ia796b06b5228cbec4cfe8d78a500f967181d8c1f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/5540
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Natasha Lee <natlee@microsoft.com>
diff --git a/dawn.json b/dawn.json
index 0b132a1..d4fec2f 100644
--- a/dawn.json
+++ b/dawn.json
@@ -986,6 +986,9 @@
                 "args": [
                     {"name": "descriptor", "type": "texture view descriptor", "annotation": "const*"}
                 ]
+            },
+            {
+                "name": "destroy"
             }
         ]
     },