Explicitly reset mDeleter when moving Blob

It's not automatically cleared to empty when moving on ChromeOS, so
the same mDeleter can be executed more than once.

Bug: chromium:1348193

Change-Id: If96a73f0b9bf62b2212a9f47108c465d6c911617
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/97865
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Austin Eng <enga@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>

src/dawn/native/Blob.cpp

@@ -53,6 +53,7 @@ Blob::Blob(uint8_t* data, size_t size, std::function<void()> deleter)
 
 Blob::Blob(Blob&& rhs) : mData(rhs.mData), mSize(rhs.mSize) {
     mDeleter = std::move(rhs.mDeleter);
+    rhs.mDeleter = nullptr;
 }
 
 Blob& Blob::operator=(Blob&& rhs) {
@@ -62,6 +63,7 @@ Blob& Blob::operator=(Blob&& rhs) {
         mDeleter();
     }
     mDeleter = std::move(rhs.mDeleter);
+    rhs.mDeleter = nullptr;
     return *this;
 }