C bindings: Implement _DeepCopy() & some unittests.

mojo/public/c/bindings/struct.h

Index: mojo/public/c/bindings/struct.h
diff --git a/mojo/public/c/bindings/struct.h b/mojo/public/c/bindings/struct.h
index 67798c3c3daaa3abe27c7a81d740de2fe1bfbc80..0fb188646abc7bf48a3db119ddc2695ee13cc322 100644
--- a/mojo/public/c/bindings/struct.h
+++ b/mojo/public/c/bindings/struct.h
@@ -88,6 +88,21 @@ MojomValidationResult MojomStruct_Validate(
     uint32_t in_num_handles,
     struct MojomValidationContext* inout_context);
 
+// Creates a new copy of |in_struct| using |buffer| to allocate space.
+// Recursively creates new copies of any references from |in_struct|, and
+// updates the references to point to the new copies. All handles are moved
+// from |in_struct| to the new copy (the copies in |in_struct| are assigned an
+// invalid handle value). This operation is useful if you want to linearize
+// |in_struct| using the buffer backed by |buffer|. The new copy of the struct
+// is returned, and can then be encoded.
+// |buffer|: A mojom buffer used to allocate space for the new struct.

[viettrungluu, 2016/08/02 20:15:06]

(Same questions about the amount of space required and failures apply here and
elsewhere too.)

+// |in_type_desc|: Describes the pointer and handle fields of the mojom struct.
+// |in_struct|: The unencoded mojom struct to be copied.
+struct MojomStructHeader* MojomStruct_DeepCopy(
+    struct MojomBuffer* buffer,
+    const struct MojomTypeDescriptorStruct* in_type_desc,
+    struct MojomStructHeader* in_struct);
+
 MOJO_END_EXTERN_C
 
 #endif  // MOJO_PUBLIC_C_BINDINGS_STRUCT_H_