Revert of Revert renderer IPC::Channel acquisition via shell connection

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 10612ce9b76a31afc51f725317be55b51ced954a..0ce8b2249b2afb8c3331cf302b1678e93a37ee81 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -834,7 +834,7 @@
         g_renderer_main_thread_factory(InProcessChildThreadParams(
             channel_id,
             BrowserThread::GetTaskRunnerForThread(BrowserThread::IO),
-            channel_token_, mojo_child_connection_->service_token())));
+            std::string(), mojo_child_connection_->service_token())));
 
     base::Thread::Options options;
 #if defined(OS_WIN) && !defined(OS_MACOSX)
@@ -894,11 +894,11 @@
     const std::string& channel_id) {
   scoped_refptr<base::SingleThreadTaskRunner> runner =
       BrowserThread::GetTaskRunnerForThread(BrowserThread::IO);
-  channel_token_ = mojo::edk::GenerateRandomToken();
-  mojo::ScopedMessagePipeHandle handle =
-      mojo::edk::CreateParentMessagePipe(channel_token_, child_token_);
+  IPC::mojom::ChannelBootstrapPtr bootstrap;
+  GetRemoteInterfaces()->GetInterface(&bootstrap);
   std::unique_ptr<IPC::ChannelFactory> channel_factory =
-      IPC::ChannelMojo::CreateServerFactory(std::move(handle), runner);
+      IPC::ChannelMojo::CreateServerFactory(
+          bootstrap.PassInterface().PassHandle(), runner);
 
   // Do NOT expand ifdef or run time condition checks here! Synchronous
   // IPCs from browser process are banned. It is only narrowly allowed
@@ -1433,11 +1433,6 @@
 #endif
 
   AppendCompositorCommandLineFlags(command_line);
-
-  if (!channel_token_.empty()) {
-    command_line->AppendSwitchASCII(
-        switches::kMojoChannelToken, channel_token_);
-  }
 
   command_line->AppendSwitchASCII(switches::kMojoApplicationChannelToken,
                                   mojo_child_connection_->service_token());