[DO NOT LAND] Example snippet for crbug.com/729447.

third_party/WebKit/Source/core/style/StyleTransformData.cpp

Index: third_party/WebKit/Source/core/style/StyleTransformData.cpp
diff --git a/third_party/WebKit/Source/core/style/StyleTransformData.cpp b/third_party/WebKit/Source/core/style/StyleTransformData.cpp
index 0d13e536a56634109b002b01f071b78d0aae5a7d..68ce62477fb71d058151392f34f0cf15452198f1 100644
--- a/third_party/WebKit/Source/core/style/StyleTransformData.cpp
+++ b/third_party/WebKit/Source/core/style/StyleTransformData.cpp
@@ -61,4 +61,29 @@ bool StyleTransformData::Has3DTransform() const {
          (scale_ && scale_->Z() != 1);
 }
 
+// Simple GC'd class
+struct Cat : public GarbageCollected<Cat> {  // (A)
+  DECLARE_TRACE();
+};
+
+// Simple class that uses a GC'd class.
+template <class T>
+struct Ptr {
+  T* ptr;
+};
+
+// Simple overloaded template functions
+template <class T>
+void meow(const T*) {}
+
+template <class T>
+void meow(const Ptr<T>&) {}
+
+// Calls meow with explicit template parameters.
+// Expect to call meow(const T*).
+// error: [blink-gc] Class 'Ptr<blink::Cat>' contains invalid fields.
+void boom() {
+  meow<Cat>(new Cat);  // (B)
+}
+
 }  // namespace blink