Remove indirection for vertexStage

This is to match the work in progress webgpu.h header.

Also contains a fix for the wire where it wouldn't GetExtraRequiredSize
for structures that are by-value members of other structures.

BUG=dawn:22

Change-Id: I3c706bf9cd7a550d40fd667877f032c860d0a032
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/9382
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
diff --git a/examples/CppHelloTriangle.cpp b/examples/CppHelloTriangle.cpp
index baa7937..f3af2c6 100644
--- a/examples/CppHelloTriangle.cpp
+++ b/examples/CppHelloTriangle.cpp
@@ -127,7 +127,7 @@
 
     utils::ComboRenderPipelineDescriptor descriptor(device);
     descriptor.layout = utils::MakeBasicPipelineLayout(device, &bgl);
-    descriptor.cVertexStage.module = vsModule;
+    descriptor.vertexStage.module = vsModule;
     descriptor.cFragmentStage.module = fsModule;
     descriptor.cVertexInput.bufferCount = 1;
     descriptor.cVertexInput.cBuffers[0].stride = 4 * sizeof(float);