[DevTools] Initialize InspectorSession later

Restoring InspectorSession may send protocol notifications
synchronously, so we should setup all bindings beforehand.

[email protected]

(cherry picked from commit c27cabf)

Bug: 804214
Change-Id: I68989990fe210a61251dc20047b891fa4155d596
Reviewed-on: https://chromium-review.googlesource.com/879137
Reviewed-by: Pavel Feldman <[email protected]>
Commit-Queue: Dmitry Gozman <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#531349}
Reviewed-on: https://chromium-review.googlesource.com/884510
Reviewed-by: Dmitry Gozman <[email protected]>
Cr-Commit-Position: refs/branch-heads/3325@{#72}
Cr-Branched-From: bc084a8-refs/heads/master@{#530369}

third_party/WebKit/Source/core/exported/WebDevToolsAgentImpl.cpp

@@ -319,8 +319,6 @@ WebDevToolsAgentImpl::Session::Session(
     : agent_(agent),
       frame_(agent->web_local_frame_impl_),
       binding_(this, std::move(request)) {
-  InitializeInspectorSession(reattach_state);
-
   io_session_ =
       new IOSession(Platform::Current()->GetIOTaskRunner(),
                     frame_->GetFrame()->GetTaskRunner(TaskType::kUnthrottled),
@@ -329,6 +327,8 @@ WebDevToolsAgentImpl::Session::Session(
   host_ptr_.Bind(std::move(host_ptr_info));
   host_ptr_.set_connection_error_handler(WTF::Bind(
       &WebDevToolsAgentImpl::Session::Detach, WrapWeakPersistent(this)));
+
+  InitializeInspectorSession(reattach_state);
 }
 
 void WebDevToolsAgentImpl::Session::Trace(blink::Visitor* visitor) {