Adds To/FromAPI calls for wgpu (C++) namespace structs.

Note that the objects do not have them added in this change because
they are a bit more complicated w.r.t whether we should add a refcount
or not.

Change-Id: Ie832e8923821d06d0dfcbd6a5bfdc9b2cb89dab5
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/119820
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Loko Kung <lokokung@google.com>
Reviewed-by: Austin Eng <enga@chromium.org>

generator/templates/dawn/native/dawn_platform.h

@@ -48,6 +48,23 @@ namespace {{native_namespace}} {
         inline {{as_cppType(type.name)}}* FromAPI({{as_cType(type.name)}}* rhs) {
             return reinterpret_cast<{{as_cppType(type.name)}}*>(rhs);
         }
+
+        inline const {{metadata.namespace}}::{{as_cppType(type.name)}}* ToCppAPI(const {{as_cppType(type.name)}}* rhs) {
+            return reinterpret_cast<const {{metadata.namespace}}::{{as_cppType(type.name)}}*>(rhs);
+        }
+
+        inline {{metadata.namespace}}::{{as_cppType(type.name)}}* ToCppAPI({{as_cppType(type.name)}}* rhs) {
+            return reinterpret_cast<{{metadata.namespace}}::{{as_cppType(type.name)}}*>(rhs);
+        }
+
+        inline const {{as_cppType(type.name)}}* FromCppAPI(const {{metadata.namespace}}::{{as_cppType(type.name)}}* rhs) {
+            return reinterpret_cast<const {{as_cppType(type.name)}}*>(rhs);
+        }
+
+        inline {{as_cppType(type.name)}}* FromCppAPI({{metadata.namespace}}::{{as_cppType(type.name)}}* rhs) {
+            return reinterpret_cast<{{as_cppType(type.name)}}*>(rhs);
+        }
+
     {% endfor %}
 
     {% for type in by_category["object"] %}
@@ -87,6 +104,6 @@ namespace {{native_namespace}} {
             return static_cast<{{namespace}}::{{as_cppType(type.name)}}>(rhs);
         }
     {% endfor %}
-}
+}  // namespace {{native_namespace}}
 
 #endif  // {{NATIVE_DIR}}_{{PREFIX}}_PLATFORM_AUTOGEN_H_