[mojo] Don't CHECK fail when a Mojo channel isn't available for a child process.

content/child/child_thread_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/child/child_thread_impl.h"
 
 #include <signal.h>
 #include <string>
 #include <utility>
 
@@ skipping 218 matching lines @@
 void InitializeMojoIPCChannel() {
   mojo::edk::ScopedPlatformHandle platform_channel;
 #if defined(OS_WIN)
   platform_channel =
       mojo::edk::PlatformChannelPair::PassClientHandleFromParentProcess(
           *base::CommandLine::ForCurrentProcess());
 #elif defined(OS_POSIX)
   platform_channel.reset(mojo::edk::PlatformHandle(
       base::GlobalDescriptors::GetInstance()->Get(kMojoIPCChannel)));
 #endif
-  CHECK(platform_channel.is_valid());
+  // Mojo isn't supported on all child process types.
+  // TODO(crbug.com/604282): Support Mojo in the remaining processes.
+  if (!platform_channel.is_valid())
+    return;
   mojo::edk::SetParentPipeHandle(std::move(platform_channel));
 }
 
 }  // namespace
 
 ChildThread* ChildThread::Get() {
   return ChildThreadImpl::current();
 }
 
 ChildThreadImpl::Options::Options()
@@ skipping 470 matching lines @@
 void ChildThreadImpl::EnsureConnected() {
   VLOG(0) << "ChildThreadImpl::EnsureConnected()";
   base::Process::Current().Terminate(0, false);
 }
 
 bool ChildThreadImpl::IsInBrowserProcess() const {
   return browser_process_io_runner_;
 }
 
 }  // namespace content