Add field-initializing constructors to generated mojo structs.

mojo/public/cpp/bindings/tests/pickled_types_blink.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_TESTS_PICKLED_TYPES_BLINK_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_TESTS_PICKLED_TYPES_BLINK_H_
 
 #include <stddef.h>
 
 #include <string>
@@ skipping 33 matching lines @@
     DCHECK_GE(foo, 0);
     foo_ = foo;
   }
 
   int bar() const { return bar_; }
   void set_bar(int bar) {
     DCHECK_GE(bar, 0);
     bar_ = bar;
   }
 
+  // The |baz| field should never be serialized.
+  int baz() const { return baz_; }
+  void set_baz(int baz) { baz_ = baz; }
+
  private:
   int foo_ = 0;
   int bar_ = 0;
+  int baz_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(PickledStructBlink);
 };
 
 }  // namespace test
 }  // namespace mojo
 
 namespace IPC {
 
 template <>
 struct ParamTraits<mojo::test::PickledStructBlink> {
   using param_type = mojo::test::PickledStructBlink;
 
   static void GetSize(base::PickleSizer* sizer, const param_type& p);
   static void Write(base::Pickle* m, const param_type& p);
   static bool Read(const base::Pickle* m,
                    base::PickleIterator* iter,
                    param_type* r);
   static void Log(const param_type& p, std::string* l) {}
 };
 
 }  // namespace IPC
 
 IPC_ENUM_TRAITS_MAX_VALUE(mojo::test::PickledEnumBlink,
                           mojo::test::PickledEnumBlink::VALUE_1)
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_TESTS_PICKLED_TYPES_BLINK_H_