[dawn][metal] ArgBufs: avoid creating zero-sized argbufs

Also remove a TODO that was done in
ccc243cd4a3bd33fdb2ae5da97bb7bc13ddf8369.

Test: BindGroupTests.MultipleEntryPointsWithMultipleNonZeroGroups
Bug: 363031535
Change-Id: I21b5124cb7c83a7456f49ae6d12d64f7534bf34f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/292615
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

src/dawn/native/metal/BindGroupMTL.mm

diff --git a/src/dawn/native/metal/BindGroupMTL.mm b/src/dawn/native/metal/BindGroupMTL.mm
index f9deb10..19a0fa2 100644
--- a/src/dawn/native/metal/BindGroupMTL.mm
+++ b/src/dawn/native/metal/BindGroupMTL.mm
@@ -58,13 +58,17 @@
         return {};
     }
 
-    // TODO(crbug.com/363031535): The argument buffers should probably work in some kind of pool
+    // TODO(crbug.com/477311786): The argument buffers should probably work in some kind of pool
     // instead of being allocated here
 
     auto layout = ToBackend(GetLayout());
 
     auto encoder = layout->GetArgumentEncoder();
     NSUInteger argumentBufferLength = [*encoder encodedLength];
+    // Avoid zero-sized buffers by rounding up the size.
+    if (argumentBufferLength == 0) {
+        argumentBufferLength = 8;
+    }
 
     mArgumentBuffer = AcquireNSPRef([device->GetMTLDevice() newBufferWithLength:argumentBufferLength
                                                                         options:0]);
@@ -83,8 +87,6 @@
 
         // Note, if a resource is destroyed, we will write nil to that slot.
         // Validation should ensure we never actually try to use it.
-        // TODO(crbug.com/363031535): The buffers, samplers and textures in the MatchVariant need to
-        // have resource usage tracking added.
         MatchVariant(
             bindingInfo.bindingLayout,
             [&](const BufferBindingInfo& layout) {