IPC::Message -> base::Pickle

This changes consumers of IPC::Message to generally refer
refer to base::Pickle instead when performing serialization
and deserialization operations. The few specific instances
where the IPC::Message interface (Read/WriteAttachent) is
needed can safely be static_cast'd, as IPC::Message is the
only public subclass of base::Pickle.

The purpose of this change is to facilitate the transition
to Mojo IPC, as we've trained the Mojo bindings layer to
use existing ParamTraits<T> parameterized over base::Pickle.

To support this base::Pickle has had some stub interfaces
added for WriteAttachment and ReadAttachment, along with a
Pickle::Attachment.

A follow-up patch will add sizing traits to the standard
IPC_STRUCT macros, enabling the majority of Chrome IPC
structs to be carried over Mojo message pipes as-is.

BUG=577685
R=jam@chromium.org

Review URL: https://codereview.chromium.org/1659003003

Cr-Commit-Position: refs/heads/master@{#373323}

2 files changed, 14 insertions, 8 deletions

diff --git a/chromecast/common/media/cma_param_traits.cc b/chromecast/common/media/cma_param_traits.cc
index 4c15ac8..f27043d 100644
--- a/chromecast/common/media/cma_param_traits.cc
+++ b/chromecast/common/media/cma_param_traits.cc
@@ -30,7 +30,8 @@ IPC_ENUM_TRAITS_MAX_VALUE(media::VideoPixelFormat, media::PIXEL_FORMAT_MAX)
 namespace IPC {
 
 void ParamTraits<media::AudioDecoderConfig>::Write(
-    Message* m, const media::AudioDecoderConfig& p) {
+    base::Pickle* m,
+    const media::AudioDecoderConfig& p) {
   WriteParam(m, p.codec());
   WriteParam(m, p.sample_format());
   WriteParam(m, p.channel_layout());
@@ -40,7 +41,7 @@ void ParamTraits<media::AudioDecoderConfig>::Write(
 }
 
 bool ParamTraits<media::AudioDecoderConfig>::Read(
-    const Message* m,
+    const base::Pickle* m,
     base::PickleIterator* iter,
     media::AudioDecoderConfig* r) {
   media::AudioCodec codec;
@@ -65,7 +66,8 @@ void ParamTraits<media::AudioDecoderConfig>::Log(
 }
 
 void ParamTraits<media::VideoDecoderConfig>::Write(
-    Message* m, const media::VideoDecoderConfig& p) {
+    base::Pickle* m,
+    const media::VideoDecoderConfig& p) {
   WriteParam(m, p.codec());
   WriteParam(m, p.profile());
   WriteParam(m, p.format());
@@ -78,7 +80,7 @@ void ParamTraits<media::VideoDecoderConfig>::Write(
 }
 
 bool ParamTraits<media::VideoDecoderConfig>::Read(
-    const Message* m,
+    const base::Pickle* m,
     base::PickleIterator* iter,
     media::VideoDecoderConfig* r) {
   media::VideoCodec codec;
diff --git a/chromecast/common/media/cma_param_traits.h b/chromecast/common/media/cma_param_traits.h
index 106012b..c8609a5 100644
--- a/chromecast/common/media/cma_param_traits.h
+++ b/chromecast/common/media/cma_param_traits.h
@@ -17,16 +17,20 @@ namespace IPC {
 template <>
 struct ParamTraits<media::AudioDecoderConfig> {
   typedef media::AudioDecoderConfig param_type;
-  static void Write(Message* m, const param_type& p);
-  static bool Read(const Message* m, base::PickleIterator* iter, param_type* r);
+  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);
 };
 
 template <>
 struct ParamTraits<media::VideoDecoderConfig> {
   typedef media::VideoDecoderConfig param_type;
-  static void Write(Message* m, const param_type& p);
-  static bool Read(const Message* m, base::PickleIterator* iter, param_type* r);
+  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);
 };