Implement argument validation for chrome.cast.channel.{open,send}

chrome/browser/extensions/api/cast_channel/cast_channel_api.cc

Index: chrome/browser/extensions/api/cast_channel/cast_channel_api.cc
diff --git a/chrome/browser/extensions/api/cast_channel/cast_channel_api.cc b/chrome/browser/extensions/api/cast_channel/cast_channel_api.cc
index d1a84e4a31261a8f61178ce6c93e854619311df5..0fe631fb1aabd8bb0da16e1975559c82f763a119 100644
--- a/chrome/browser/extensions/api/cast_channel/cast_channel_api.cc
+++ b/chrome/browser/extensions/api/cast_channel/cast_channel_api.cc
@@ -280,6 +280,8 @@ bool CastChannelOpenFunction::Prepare() {
       connect_info_.reset(new ConnectInfo);
       if (!ParseChannelUrl(GURL(cast_url), connect_info_.get())) {
         connect_info_.reset();
+        SetError("Invalid Cast URL " + cast_url);
+        return false;
       }
       break;
     case base::Value::TYPE_DICTIONARY:
@@ -291,9 +293,13 @@ bool CastChannelOpenFunction::Prepare() {
   if (connect_info_.get()) {
     channel_auth_ = connect_info_->auth;
     ip_endpoint_.reset(ParseConnectInfo(*connect_info_));
-    return ip_endpoint_.get() != NULL;
+    if (!ip_endpoint_.get()) {
+      SetError("Invalid connect_info");
+    }
+  } else {
+    SetError("Invalid connect_info");
   }
-  return false;
+  return ip_endpoint_.get() != NULL;
 }
 
 void CastChannelOpenFunction::AsyncWorkStart() {
@@ -319,7 +325,27 @@ CastChannelSendFunction::~CastChannelSendFunction() { }
 bool CastChannelSendFunction::Prepare() {
   params_ = Send::Params::Create(*args_);
   EXTENSION_FUNCTION_VALIDATE(params_.get());
-  return true;
+  if (params_->message.namespace_.empty()) {
+    SetError("message_info.namespace_ is required");
+    return false;
+  }
+  if (params_->message.source_id.empty()) {
+    SetError("message_info.source_id is required");
+    return false;
+  }
+  if (params_->message.destination_id.empty()) {
+    SetError("message_info.destination_id is required");
+    return false;
+  }
+  switch (params_->message.data->GetType()) {
+    case base::Value::TYPE_STRING:
+    case base::Value::TYPE_BINARY:
+      return true;

[imcheng, 2014/04/24 22:13:18]

super nit: I'd prefer to see validation logic return true at the very end:

switch (params_->message.data->GetType()) {
  case base::Value::TYPE_STRING:
  case base::Value::TYPE_BINARY:
    break;
  default:
    SetError("Invalid type of message_info.data");
    return false;
}
return true;


Because that way it will be less error-prone to append other validation logic in
the future.

+    default:
+      break;
+  }
+  SetError("Invalid type of message_info.data");
+  return false;
 }
 
 void CastChannelSendFunction::AsyncWorkStart() {