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..a780e880cbf67c52d44d8d42efd643358e445360 100644
--- a/mojo/public/tools/bindings/generators/mojom_cpp_generator.py
+++ b/mojo/public/tools/bindings/generators/mojom_cpp_generator.py
@@ -482,6 +482,17 @@ 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):
+    # Types that are neither copyable nor movable can't be passed to a struct
+    # constructor so any constructors containing such a kind are skipped.
+    if (mojom.IsStructKind(field.kind) and IsTypemappedKind(field.kind) and

[yzshen1, 2017/02/14 17:21:53]

I think there is no need to check IsStructKind(), right? At least we should take
unions into account as well.

[Sam McNally, 2017/02/15 06:35:49]

Done.

+        _current_typemap[GetFullMojomNameForKind(field.kind)]["emplace_only"]):
+      return i
+  return len(kind.fields) + 1
+
+
 def GetContainerValidateParamsCtorArgs(kind):
   if mojom.IsStringKind(kind):
     expected_num_elements = 0
@@ -571,6 +582,7 @@ 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,