libchromeos: Move Dictionary class into its own header file

Moved chromeos::dbus_utils::Dictionary type alias into its
own header file (chromeos/dictionary.h) and promoting it to the
top level namespace (chromeos).

So now it becomes chromeos::VariantDictionary and it is now
independent from D-Bus data serialization.

BUG=None
TEST=FEATURE=test emerge-link libchromeos buffet

Change-Id: Ibad63fd4168d77b9a4b80c7800016510f87ae33d
Reviewed-on: https://chromium-review.googlesource.com/219413
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/buffet/commands/dbus_command_proxy_unittest.cc b/buffet/commands/dbus_command_proxy_unittest.cc
index d4550a5..34d9f1d 100644
--- a/buffet/commands/dbus_command_proxy_unittest.cc
+++ b/buffet/commands/dbus_command_proxy_unittest.cc
@@ -24,8 +24,8 @@
 
 using buffet::unittests::CreateDictionaryValue;
 using chromeos::dbus_utils::AsyncEventSequencer;
-using chromeos::dbus_utils::Dictionary;
 using chromeos::dbus_utils::ExportedObjectManager;
+using chromeos::VariantDictionary;
 
 namespace buffet {
 
@@ -118,7 +118,7 @@
     return command_proxy_->progress_.value();
   }
 
-  Dictionary GetParameters() const {
+  VariantDictionary GetParameters() const {
     return command_proxy_->parameters_.value();
   }
 
@@ -175,7 +175,7 @@
 };
 
 TEST_F(DBusCommandProxyTest, Init) {
-  Dictionary params = {
+  VariantDictionary params = {
     {"height", int32_t{53}},
     {"_jumpType", std::string{"_withKick"}},
   };
@@ -192,7 +192,8 @@
             GetPropertyValue<std::string>(dbus_constants::kCommandStatus));
   EXPECT_EQ(0, GetPropertyValue<int32_t>(dbus_constants::kCommandProgress));
   EXPECT_EQ(params,
-            GetPropertyValue<Dictionary>(dbus_constants::kCommandParameters));
+            GetPropertyValue<VariantDictionary>(
+                dbus_constants::kCommandParameters));
 }
 
 TEST_F(DBusCommandProxyTest, SetProgress) {