Special-case GetDefaultQueue in the wire

Reland with a fix where commands only start being serialized by the
device after the first GetDevice() is called, not in the constructor.

This makes it so calling GetDefaultQueue always returns the same
object. It required updating various WireTests to account for the
additional wire calls.

Bug: dawn:22
Change-Id: Ibe43d84b25100f58a9ec5029a9341e400aec97f6
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/19982
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>

src/dawn_wire/client/Client.cpp

@@ -21,7 +21,6 @@ namespace dawn_wire { namespace client {
 
     Client::Client(CommandSerializer* serializer, MemoryTransferService* memoryTransferService)
         : ClientBase(),
-          mDevice(DeviceAllocator().New(this)->object.get()),
           mSerializer(serializer),
           mMemoryTransferService(memoryTransferService) {
         if (mMemoryTransferService == nullptr) {
@@ -32,7 +31,16 @@ namespace dawn_wire { namespace client {
     }
 
     Client::~Client() {
-        DeviceAllocator().Free(mDevice);
+        if (mDevice != nullptr) {
+            DeviceAllocator().Free(mDevice);
+        }
+    }
+
+    WGPUDevice Client::GetDevice() {
+        if (mDevice == nullptr) {
+            mDevice = DeviceAllocator().New(this)->object.get();
+        }
+        return reinterpret_cast<WGPUDeviceImpl*>(mDevice);
     }
 
     ReservedTexture Client::ReserveTexture(WGPUDevice cDevice) {
@@ -57,8 +65,12 @@ namespace dawn_wire { namespace client {
     }
 
     void Client::Disconnect() {
-        if (!mIsDisconnected) {
-            mIsDisconnected = true;
+        if (mIsDisconnected) {
+            return;
+        }
+
+        mIsDisconnected = true;
+        if (mDevice != nullptr) {
             mDevice->HandleDeviceLost("GPU connection lost");
         }
     }