Revert of Use a token to initialise ChannelMojo and MojoApplication everywhere.

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 7b5f9ff57367f8073f1ad0d206db307da2d413b8..1befcec16fedbdf51df06ead6c915b0717935fa2 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -126,6 +126,8 @@
 #include "content/common/frame_messages.h"
 #include "content/common/gpu_host_messages.h"
 #include "content/common/in_process_child_thread_params.h"
+#include "content/common/mojo/channel_init.h"
+#include "content/common/mojo/mojo_messages.h"
 #include "content/common/mojo/mojo_shell_connection_impl.h"
 #include "content/common/render_process_messages.h"
 #include "content/common/resource_messages.h"
@@ -730,6 +732,9 @@
       content::BrowserThread::IO));
 #endif
 
+  // Setup the Mojo channel.
+  mojo_application_host_->Init();
+
   // Call the embedder first so that their IPC filters have priority.
   GetContentClient()->browser()->RenderProcessWillLaunch(this);
 
@@ -749,7 +754,7 @@
             channel_id,
             BrowserThread::UnsafeGetMessageLoopForThread(BrowserThread::IO)
                 ->task_runner(),
-            mojo_channel_token_, mojo_application_host_->GetToken())));
+            in_process_renderer_handle_.release())));
 
     base::Thread::Options options;
 #if defined(OS_WIN) && !defined(OS_MACOSX)
@@ -808,9 +813,16 @@
       BrowserThread::GetMessageLoopProxyForThread(BrowserThread::IO);
   if (ShouldUseMojoChannel()) {
     VLOG(1) << "Mojo Channel is enabled on host";
-    mojo_channel_token_ = mojo::edk::GenerateRandomToken();
-    mojo::ScopedMessagePipeHandle handle =
-        mojo::edk::CreateParentMessagePipe(mojo_channel_token_);
+    mojo::ScopedMessagePipeHandle handle;
+
+    if (run_renderer_in_process()) {
+      mojo::MessagePipe pipe;
+      handle = std::move(pipe.handle0);
+      in_process_renderer_handle_ = std::move(pipe.handle1);
+    } else {
+      mojo_channel_token_ = mojo::edk::GenerateRandomToken();
+      handle = mojo::edk::CreateParentMessagePipe(mojo_channel_token_);
+    }
 
     // Do NOT expand ifdef or run time condition checks here! Synchronous
     // IPCs from browser process are banned. It is only narrowly allowed
@@ -1369,8 +1381,6 @@
     command_line->AppendSwitchASCII(switches::kMojoChannelToken,
                                     mojo_channel_token_);
   }
-  command_line->AppendSwitchASCII(switches::kMojoApplicationChannelToken,
-                                  mojo_application_host_->GetToken());
 }
 
 void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
@@ -2608,6 +2618,11 @@
                                          Source<RenderProcessHost>(this),
                                          NotificationService::NoDetails());
 
+  // Allow Mojo to be setup before the renderer sees any Chrome IPC messages.
+  // This way, Mojo can be safely used from the renderer in response to any
+  // Chrome IPC message.
+  mojo_application_host_->Activate(this, GetHandle());
+
   while (!queued_messages_.empty()) {
     Send(queued_messages_.front());
     queued_messages_.pop();