Fix device_pool refactor (#3469)

The old version made one device with no descriptor.
If that fail then it stopped creating any devices period.

The previous refactor was bad in that if the any device
failed it would just stop making devices.

This one is simplified. It just used the pool as a pool.
There is no special handling for failed devices.

Author: greggman

src/webgpu/util/device_pool.ts

@@ -22,7 +22,7 @@ class FeaturesNotSupported extends Error {}
 export class TestOOMedShouldAttemptGC extends Error {}
 
 export class DevicePool {
-  private holders: 'uninitialized' | 'failed' | DescriptorToHolderMap = 'uninitialized';
+  private holders = new DescriptorToHolderMap();
 
   async requestAdapter(recorder: TestCaseRecorder) {
     const gpu = getGPU(recorder);
@@ -36,28 +36,7 @@ export class DevicePool {
     adapter: GPUAdapter,
     descriptor?: UncanonicalizedDeviceDescriptor
   ): Promise<DeviceProvider> {
-    let holder;
-    if (this.holders === 'uninitialized') {
-      this.holders = new DescriptorToHolderMap();
-    }
-
-    let errorMessage = '';
-    if (this.holders !== 'failed') {
-      try {
-        holder = await this.holders.getOrCreate(adapter, descriptor);
-      } catch (ex) {
-        this.holders = 'failed';
-        if (ex instanceof Error) {
-          errorMessage = ` with ${ex.name} "${ex.message}"`;
-        }
-      }
-    }
-
-    assert(
-      this.holders !== 'failed',
-      `WebGPU device failed to initialize${errorMessage}; not retrying`
-    );
-    assert(!!holder);
+    const holder = await this.holders.getOrCreate(adapter, descriptor);
     assert(holder.state === 'free', 'Device was in use on DevicePool.acquire');
     holder.state = 'acquired';
     holder.beginTestScope();