Add field-initializing constructors to generated mojo structs.

mojo/public/tools/bindings/generators/mojom_cpp_generator.py

Index: mojo/public/tools/bindings/generators/mojom_cpp_generator.py
diff --git a/mojo/public/tools/bindings/generators/mojom_cpp_generator.py b/mojo/public/tools/bindings/generators/mojom_cpp_generator.py
index c75013badf88a19cab5a678a1b77174e20c877fc..311916a56a199c962f9fc0ef2160c63cc3051c7b 100644
--- a/mojo/public/tools/bindings/generators/mojom_cpp_generator.py
+++ b/mojo/public/tools/bindings/generators/mojom_cpp_generator.py
@@ -482,6 +482,18 @@ def ShouldInlineUnion(union):
       mojom.IsReferenceKind(field.kind) and not mojom.IsStringKind(field.kind)
            for field in union.fields)
 
+
+def GetNumConstructorParams(kind):
+  for i, field in enumerate(kind.fields):
+    # mojo.common.mojom.LegacyListValue is neither copyable nor movable so can't

[yzshen1, 2017/02/13 17:45:53]

It is unfortunate to have a special case for this.
Could we consider a black list in the typemap configuration, or have a new
attribute similar to [move_only] to indicate something
non-copyable&&non-movable?

[Sam McNally, 2017/02/14 02:32:24]

Done.

+    # be passed to a struct constructor so any constructors containing this
+    # struct are skipped.
+    if (mojom.IsStructKind(field.kind) and GetFullMojomNameForKind(
+        field.kind) == "mojo.common.mojom.LegacyListValue"):
+      return i
+  return len(kind.fields) + 1
+
+
 def GetContainerValidateParamsCtorArgs(kind):
   if mojom.IsStringKind(kind):
     expected_num_elements = 0
@@ -571,6 +583,7 @@ class Generator(generator.Generator):
     "is_struct_kind": mojom.IsStructKind,
     "is_typemapped_kind": IsTypemappedKind,
     "is_union_kind": mojom.IsUnionKind,
+    "num_constructor_params": GetNumConstructorParams,
     "passes_associated_kinds": mojom.PassesAssociatedKinds,
     "stylize_method": generator.StudlyCapsToCamel,
     "under_to_camel": generator.UnderToCamel,