AddTo will return AddToTypeProxy for convenience

Change-Id: If86496af0c68af31a3e0c618b0fae861975a4ebf
Reviewed-on: https://weave-review.googlesource.com/2321
Reviewed-by: Vitaly Buka <vitalybuka@google.com>

src/commands/command_instance.cc

diff --git a/src/commands/command_instance.cc b/src/commands/command_instance.cc
index dba14c4..fc9b0e7 100644
--- a/src/commands/command_instance.cc
+++ b/src/commands/command_instance.cc
@@ -37,10 +37,10 @@
 bool ReportInvalidStateTransition(ErrorPtr* error,
                                   Command::State from,
                                   Command::State to) {
-  Error::AddToPrintf(error, FROM_HERE, errors::commands::kInvalidState,
-                     "State switch impossible: '%s' -> '%s'",
-                     EnumToString(from).c_str(), EnumToString(to).c_str());
-  return false;
+  return Error::AddToPrintf(error, FROM_HERE, errors::commands::kInvalidState,
+                            "State switch impossible: '%s' -> '%s'",
+                            EnumToString(from).c_str(),
+                            EnumToString(to).c_str());
 }
 
 }  // namespace
@@ -152,10 +152,9 @@
     // Make sure the "parameters" property is actually an object.
     const base::DictionaryValue* params_dict = nullptr;
     if (!params_value->GetAsDictionary(&params_dict)) {
-      Error::AddToPrintf(error, FROM_HERE, errors::json::kObjectExpected,
-                         "Property '%s' must be a JSON object",
-                         commands::attributes::kCommand_Parameters);
-      return params;
+      return Error::AddToPrintf(error, FROM_HERE, errors::json::kObjectExpected,
+                                "Property '%s' must be a JSON object",
+                                commands::attributes::kCommand_Parameters);
     }
     params.reset(params_dict->DeepCopy());
   } else {
@@ -180,10 +179,9 @@
   // Get the command JSON object from the value.
   const base::DictionaryValue* json = nullptr;
   if (!value->GetAsDictionary(&json)) {
-    Error::AddTo(error, FROM_HERE, errors::json::kObjectExpected,
-                 "Command instance is not a JSON object");
     command_id->clear();
-    return instance;
+    return Error::AddTo(error, FROM_HERE, errors::json::kObjectExpected,
+                        "Command instance is not a JSON object");
   }
 
   // Get the command ID from 'id' property.
@@ -193,16 +191,15 @@
   // Get the command name from 'name' property.
   std::string command_name;
   if (!json->GetString(commands::attributes::kCommand_Name, &command_name)) {
-    Error::AddTo(error, FROM_HERE, errors::commands::kPropertyMissing,
-                 "Command name is missing");
-    return instance;
+    return Error::AddTo(error, FROM_HERE, errors::commands::kPropertyMissing,
+                        "Command name is missing");
   }
 
   auto parameters = GetCommandParameters(json, error);
   if (!parameters) {
-    Error::AddToPrintf(error, FROM_HERE, errors::commands::kCommandFailed,
-                       "Failed to validate command '%s'", command_name.c_str());
-    return instance;
+    return Error::AddToPrintf(
+        error, FROM_HERE, errors::commands::kCommandFailed,
+        "Failed to validate command '%s'", command_name.c_str());
   }
 
   instance.reset(new CommandInstance{command_name, origin, *parameters});