[DevTools] Rework DevToolsSession interaction with domain handlers.

content/browser/devtools/protocol/io_handler.cc

Index: content/browser/devtools/protocol/io_handler.cc
diff --git a/content/browser/devtools/protocol/io_handler.cc b/content/browser/devtools/protocol/io_handler.cc
index 1366f9fe96df63de5b7f7b150d90e5f6fff8348d..150ba99a422869fcbfe1e71cb9abf4b42ee79b69 100644
--- a/content/browser/devtools/protocol/io_handler.cc
+++ b/content/browser/devtools/protocol/io_handler.cc
@@ -20,7 +20,8 @@ namespace content {
 namespace protocol {
 
 IOHandler::IOHandler(DevToolsIOContext* io_context)
-    : io_context_(io_context)
+    : DevToolsDomainHandler(IO::Metainfo::domainName),
+      io_context_(io_context)
     , weak_factory_(this) {}
 
 IOHandler::~IOHandler() {}
@@ -30,10 +31,6 @@ void IOHandler::Wire(UberDispatcher* dispatcher) {
   IO::Dispatcher::wire(dispatcher, this);
 }
 
-Response IOHandler::Disable() {
-  return Response::OK();
-}
-
 void IOHandler::Read(
     const std::string& handle,
     Maybe<int> offset,