--- a/python/mozbuild/mozbuild/frontend/data.py
+++ b/python/mozbuild/mozbuild/frontend/data.py
@@ -176,16 +176,65 @@ class IPDLFile(SandboxDerived):
         'basename',
     )
 
     def __init__(self, sandbox, path):
         SandboxDerived.__init__(self, sandbox)
 
         self.basename = path
 
+class WebIDLFile(SandboxDerived):
+    """Describes an individual .webidl source file."""
+
+    __slots__ = (
+        'basename',
+    )
+
+    def __init__(self, sandbox, path):
+        SandboxDerived.__init__(self, sandbox)
+
+        self.basename = path
+
+class TestWebIDLFile(SandboxDerived):
+    """Describes an individual test-only .webidl source file."""
+
+    __slots__ = (
+        'basename',
+    )
+
+    def __init__(self, sandbox, path):
+        SandboxDerived.__init__(self, sandbox)
+
+        self.basename = path
+
+class PreprocessedWebIDLFile(SandboxDerived):
+    """Describes an individual .webidl source file that requires preprocessing."""
+
+    __slots__ = (
+        'basename',
+    )
+
+    def __init__(self, sandbox, path):
+        SandboxDerived.__init__(self, sandbox)
+
+        self.basename = path
+
+class GeneratedWebIDLFile(SandboxDerived):
+    """Describes an individual .webidl source file that is generated from
+    build rules."""
+
+    __slots__ = (
+        'basename',
+    )
+
+    def __init__(self, sandbox, path):
+        SandboxDerived.__init__(self, sandbox)
+
+        self.basename = path
+
 class Program(SandboxDerived):
     """Sandbox container object for PROGRAM, which is a unicode string.
 
     This class handles automatically appending BIN_SUFFIX to the PROGRAM value.
     If BIN_SUFFIX is not defined, PROGRAM is unchanged.
     Otherwise, if PROGRAM ends in BIN_SUFFIX, it is unchanged
     Otherwise, BIN_SUFFIX is appended to PROGRAM
     """