[cast_bindings] Refactor MessagePort GN targets.

This CL adds |public|, |mesage_port_fuchsia|, and |message_port_cast| to be
used for specifying a implementation for platform agnostic testing.

Bug: Internal b/168598365
Test: bindings_manager_cast_browwsertest, named_message_port_connector_fuchsia_browsertest
Change-Id: I4abfbb6a5bcfc19dbddb7634543a72f5bd288fdd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2489024
Commit-Queue: Jiawei Li <lijiawei@chromium.org>
Reviewed-by: Kevin Marshall <kmarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#822487}

components/cast/message_port/BUILD.gn

@@ -5,34 +5,59 @@
 import("//build/config/features.gni")
 
 source_set("message_port") {
+  if (is_fuchsia) {
+    public_deps = [ ":message_port_fuchsia" ]
+  } else if (is_chromecast) {
+    public_deps = [ ":message_port_cast" ]
+  }
+}
+
+source_set("public") {
   sources = [
     "message_port.cc",
     "message_port.h",
   ]
+
   deps = [
     "//base",
     "//components/cast:export",
   ]
+
   defines = [ "CAST_COMPONENT_IMPLEMENTATION" ]
 
-  if (is_fuchsia) {
-    sources += [
-      "message_port_fuchsia.cc",
-      "message_port_fuchsia.h",
-    ]
+  visibility = [ ":*" ]
+}
+
+if (is_fuchsia) {
+  source_set("message_port_fuchsia") {
+    public = [ "message_port_fuchsia.h" ]
+
+    sources = [ "message_port_fuchsia.cc" ]
+
     public_deps = [
+      ":public",
       "//fuchsia:cast_fidl",
       "//fuchsia/base",
     ]
-  } else if (is_chromecast) {
-    sources += [
-      "message_port_cast.cc",
-      "message_port_cast.h",
-    ]
-    deps += [ "//third_party/blink/public/common" ]
+
+    deps = [ "//base" ]
   }
 }
 
+source_set("message_port_cast") {
+  public = [ "message_port_cast.h" ]
+
+  sources = [ "message_port_cast.cc" ]
+
+  public_deps = [ ":public" ]
+
+  deps = [
+    ":public",
+    "//base",
+    "//third_party/blink/public/common",
+  ]
+}
+
 source_set("test_message_port_receiver") {
   testonly = true
   sources = [

components/cast/message_port/message_port.h

@@ -9,13 +9,14 @@
 #include <vector>
 
 #include "base/strings/string_piece.h"
+#include "components/cast/cast_component_export.h"
 
 namespace cast_api_bindings {
 
 // HTML5 MessagePort abstraction; allows usage of the platform MessagePort type
 // without exposing details of the message format, paired port creation, or
 // transfer of ports.
-class MessagePort {
+class CAST_COMPONENT_EXPORT MessagePort {
  public:
   // Implemented by receivers of messages from the MessagePort class.
   class Receiver {

components/cast/message_port/message_port_fuchsia.cc

@@ -195,6 +195,15 @@ class MessagePortFuchsiaServer : public MessagePortFuchsia,
 };
 }  // namespace
 
+// static
+void MessagePort::CreatePair(std::unique_ptr<MessagePort>* client,
+                             std::unique_ptr<MessagePort>* server) {
+  fidl::InterfaceHandle<fuchsia::web::MessagePort> port0;
+  fidl::InterfaceRequest<fuchsia::web::MessagePort> port1 = port0.NewRequest();
+  *client = MessagePortFuchsia::Create(std::move(port0));
+  *server = MessagePortFuchsia::Create(std::move(port1));
+}
+
 // static
 std::unique_ptr<MessagePort> MessagePortFuchsia::Create(
     fidl::InterfaceHandle<::fuchsia::web::MessagePort> handle) {
@@ -214,15 +223,6 @@ MessagePortFuchsia* MessagePortFuchsia::FromMessagePort(MessagePort* port) {
   return static_cast<MessagePortFuchsia*>(port);
 }
 
-// static
-void MessagePort::CreatePair(std::unique_ptr<MessagePort>* client,
-                             std::unique_ptr<MessagePort>* server) {
-  fidl::InterfaceHandle<fuchsia::web::MessagePort> port0;
-  fidl::InterfaceRequest<fuchsia::web::MessagePort> port1 = port0.NewRequest();
-  *client = MessagePortFuchsia::Create(std::move(port0));
-  *server = MessagePortFuchsia::Create(std::move(port1));
-}
-
 // static
 fuchsia::web::WebMessage MessagePortFuchsia::CreateWebMessage(
     base::StringPiece message,