d3d11: Fix DRAWINDIRECT buffer size

It must be at least 12 bytes according to the validation layer.

Bug: dawn:1894
Bug: dawn:1705

Change-Id: I8e4335f2cd0b616eea651a4e6e986bd7017164ed
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/139740
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Jie A Chen <jie.a.chen@intel.com>
Kokoro: Kokoro <noreply+kokoro@google.com>

src/dawn/native/d3d11/BufferD3D11.cpp

diff --git a/src/dawn/native/d3d11/BufferD3D11.cpp b/src/dawn/native/d3d11/BufferD3D11.cpp
index a534fc4..d18e9c1 100644
--- a/src/dawn/native/d3d11/BufferD3D11.cpp
+++ b/src/dawn/native/d3d11/BufferD3D11.cpp
@@ -146,6 +146,11 @@
 
     // Allocate at least 4 bytes so clamped accesses are always in bounds.
     uint64_t size = std::max(GetSize(), uint64_t(4u));
+    // The validation layer requires:
+    // ByteWidth must be 12 or larger to be used with D3D11_RESOURCE_MISC_DRAWINDIRECT_ARGS.
+    if (GetUsage() & wgpu::BufferUsage::Indirect) {
+        size = std::max(size, uint64_t(12u));
+    }
     size_t alignment = D3D11BufferSizeAlignment(GetUsage());
     // Check for overflow, bufferDescriptor.ByteWidth is a UINT.
     if (size > std::numeric_limits<UINT>::max() - alignment) {