add comments

src/common/runtime/helper/options.ts

@@ -102,7 +102,10 @@ export const kCTSOptionsInfo: OptionsInfos<CTSOptions> = {
   debug: { description: 'show more info' },
   compatibility: { description: 'run in compatibility mode' },
   forceFallbackAdapter: { description: 'pass forceFallbackAdapter: true to requestAdapter' },
-  enforceDefaultLimits: { description: 'force the adapter limits to the default limits' },
+  enforceDefaultLimits: {
+    description: `force the adapter limits to the default limits.
+Note: May fail on tests for low-power/high-performance`,
+  },
   unrollConstEvalLoops: { description: 'unroll const eval loops in WGSL' },
   powerPreference: {
     description: 'set default powerPreference for some tests',

src/common/util/navigator_gpu.ts

@@ -129,6 +129,16 @@ export function getGPU(recorder: TestCaseRecorder | null): GPU {
       this: GPUAdapter,
       desc?: GPUDeviceDescriptor | undefined
     ) {
+      // We need to enforce the default limits because even though we patched the adapter to
+      // show defaults for adapter.limits, there are tests that test we throw when we request more than the max.
+      // In other words.
+      //
+      //   adapter.requestDevice({ requiredLimits: {
+      //     maxXXX: addapter.limits.maxXXX + 1,  // should throw
+      //   });
+      //
+      // But unless we enforce this manually, it won't actual through if the adapter's
+      // true limits are higher than we patched above.
       enforceDefaultLimits(this, desc);
       return await origRequestDeviceFn.call(this, desc);
     };