Put the reference to DeviceBase in a new ObjectBase

ObjectBase will contain data that all WebGPU objects have such as a
pointer back to the device, a refcount (via inheriting from RefCounted),
a name, an error status etc.

BUG=dawn:24

Change-Id: I919e1a6d4a68811ceb6e503b2a793815c92f2528
Reviewed-on: https://dawn-review.googlesource.com/c/1620
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>

src/dawn_native/Sampler.cpp

@@ -34,7 +34,7 @@ namespace dawn_native {
 
     // SamplerBase
 
-    SamplerBase::SamplerBase(DeviceBase*, const SamplerDescriptor*) {
+    SamplerBase::SamplerBase(DeviceBase* device, const SamplerDescriptor*) : ObjectBase(device) {
     }
 
 }  // namespace dawn_native