Update default pipeline layout compatibility rules

Prevents bind group layouts created by a default pipeline layout from
being reusable with any other pipelines or layouts, as detailed in
https://github.com/gpuweb/gpuweb/pull/2068

Change-Id: Ic398eb6c6e089ac63ce6650f125dd20a9dfc8862
Bug: dawn:1094
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/63220
Commit-Queue: Brandon Jones <bajones@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

src/include/dawn_native/DawnNative.h

@@ -252,6 +252,9 @@ namespace dawn_native {
 
     DAWN_NATIVE_EXPORT uint64_t GetAllocatedSizeForTesting(WGPUBuffer buffer);
 
+    DAWN_NATIVE_EXPORT bool BindGroupLayoutBindingsEqualForTesting(WGPUBindGroupLayout a,
+                                                                   WGPUBindGroupLayout b);
+
 }  // namespace dawn_native
 
 #endif  // DAWNNATIVE_DAWNNATIVE_H_