Minor fix to build with MSVC: Removes switch with only default case

Fixes warning C4065: switch statement contains 'default' but no 'case' labels

Change-Id: If9a8f20eaeb2499f71bc25a69e545b3e8b21be4d
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/36081
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Carl Woffenden <cwoffenden@gmail.com>
diff --git a/src/dawn_native/vulkan/VulkanBackend.cpp b/src/dawn_native/vulkan/VulkanBackend.cpp
index faf17f8..8e1304f 100644
--- a/src/dawn_native/vulkan/VulkanBackend.cpp
+++ b/src/dawn_native/vulkan/VulkanBackend.cpp
@@ -91,8 +91,8 @@
 #endif  // DAWN_PLATFORM_LINUX
 
     WGPUTexture WrapVulkanImage(WGPUDevice cDevice, const ExternalImageDescriptorVk* descriptor) {
-        switch (descriptor->type) {
 #if defined(DAWN_PLATFORM_LINUX)
+        switch (descriptor->type) {
             case ExternalImageType::OpaqueFD:
             case ExternalImageType::DmaBuf: {
                 const ExternalImageDescriptorFD* fdDescriptor =
@@ -102,10 +102,12 @@
                     fdDescriptor, fdDescriptor->memoryFD, fdDescriptor->waitFDs);
                 return reinterpret_cast<WGPUTexture>(texture);
             }
-#endif  // DAWN_PLATFORM_LINUX
             default:
                 return nullptr;
         }
+#else
+        return nullptr;
+#endif  // DAWN_PLATFORM_LINUX
     }
 
     bool ExportVulkanImage(WGPUTexture cTexture,
@@ -114,8 +116,8 @@
         if (cTexture == nullptr) {
             return false;
         }
-        switch (info->type) {
 #if defined(DAWN_PLATFORM_LINUX)
+        switch (info->type) {
             case ExternalImageType::OpaqueFD:
             case ExternalImageType::DmaBuf: {
                 Texture* texture = reinterpret_cast<Texture*>(cTexture);
@@ -124,10 +126,12 @@
                 return device->SignalAndExportExternalTexture(texture, desiredLayout, fdInfo,
                                                               &fdInfo->semaphoreHandles);
             }
-#endif  // DAWN_PLATFORM_LINUX
             default:
                 return false;
         }
+#else
+        return false;
+#endif  // DAWN_PLATFORM_LINUX
     }
 
 }}  // namespace dawn_native::vulkan