Bug 1859825: Ensure that WebGPU Buffers are only dropped once. r=webgpu-reviewers,nical

In addition to moving the valid check earlier in Buffer::Drop, this
patch also ensures that Device clears the tracked buffers set after they
have been unmapped, and cleans up the error handling in Device::GetLost.

Differential Revision: https://phabricator.services.mozilla.com/D191565

dom/webgpu/Buffer.cpp

@@ -133,6 +133,12 @@ already_AddRefed<Buffer> Buffer::Create(Device* aDevice, RawId aDeviceId,
 }
 
 void Buffer::Drop() {
+  if (!mValid) {
+    return;
+  }
+
+  mValid = false;
+
   AbortMapRequest();
 
   if (mMapped && !mMapped->mArrayBuffers.IsEmpty()) {
@@ -146,13 +152,11 @@ void Buffer::Drop() {
   }
   mMapped.reset();
 
-  if (mValid && GetDevice().IsBridgeAlive()) {
-    GetDevice().GetBridge()->SendBufferDrop(mId);
-  }
-
   GetDevice().UntrackBuffer(this);
 
-  mValid = false;
+  if (GetDevice().IsBridgeAlive()) {
+    GetDevice().GetBridge()->SendBufferDrop(mId);
+  }
 }
 
 void Buffer::SetMapped(BufferAddress aOffset, BufferAddress aSize,

dom/webgpu/Device.cpp

@@ -105,6 +105,7 @@ void Device::GetLabel(nsAString& aValue) const { aValue = mLabel; }
 void Device::SetLabel(const nsAString& aLabel) { mLabel = aLabel; }
 
 dom::Promise* Device::GetLost(ErrorResult& aRv) {
+  aRv = NS_OK;
   if (!mLostPromise) {
     mLostPromise = dom::Promise::Create(GetParentObject(), aRv);
     if (mLostPromise && !mBridge->CanSend()) {
@@ -118,7 +119,7 @@ dom::Promise* Device::GetLost(ErrorResult& aRv) {
 
 void Device::ResolveLost(Maybe<dom::GPUDeviceLostReason> aReason,
                          const nsAString& aMessage) {
-  ErrorResult rv;
+  IgnoredErrorResult rv;
   dom::Promise* lostPromise = GetLost(rv);
   if (!lostPromise) {
     // Promise doesn't exist? Maybe out of memory.
@@ -374,6 +375,8 @@ void Device::Destroy() {
     for (const auto& buffer : mTrackedBuffers) {
       buffer->Unmap(jsapi.cx(), rv);
     }
+
+    mTrackedBuffers.Clear();
   }
 
   mBridge->SendDeviceDestroy(mId);