Fix a bug with D3D12 buffer alignment computation

We should use D3D12_CONSTANT_BUFFER_DATA_PLACEMENT_ALIGNMENT
if the usage *contains* Uniform usage, not if it is exactly
equal.

Fixed: dawn:1085
Change-Id: I540081e550c9e88efeb08169cecdc40b68d36d14
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/62242
Commit-Queue: Austin Eng <enga@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

src/include/dawn_native/DawnNative.h

@@ -250,6 +250,8 @@ namespace dawn_native {
 
     DAWN_NATIVE_EXPORT const char* GetObjectLabelForTesting(void* objectHandle);
 
+    DAWN_NATIVE_EXPORT uint64_t GetAllocatedSizeForTesting(WGPUBuffer buffer);
+
 }  // namespace dawn_native
 
 #endif  // DAWNNATIVE_DAWNNATIVE_H_