Always use ChannelMojo for content child processes.

content/common/in_process_child_thread_params.h

Index: content/common/in_process_child_thread_params.h
diff --git a/content/common/in_process_child_thread_params.h b/content/common/in_process_child_thread_params.h
index 4bc7deafe3c46f911871ca2aac5177c47b2b75c3..e4b673c8306dbfdd1e42794a6d86e0ef44184322 100644
--- a/content/common/in_process_child_thread_params.h
+++ b/content/common/in_process_child_thread_params.h
@@ -18,14 +18,11 @@ namespace content {
 // ChnanelMojo, an IPC channel name to open.
 class CONTENT_EXPORT InProcessChildThreadParams {
  public:
-  InProcessChildThreadParams(
-      const std::string& channel_name,
-      scoped_refptr<base::SequencedTaskRunner> io_runner,
-      const std::string& application_token = std::string());
+  InProcessChildThreadParams(scoped_refptr<base::SequencedTaskRunner> io_runner,
+                             const std::string& application_token);
   InProcessChildThreadParams(const InProcessChildThreadParams& other);
   ~InProcessChildThreadParams();
 
-  const std::string& channel_name() const { return channel_name_; }
   scoped_refptr<base::SequencedTaskRunner> io_runner() const {
     return io_runner_;
   }
@@ -34,7 +31,6 @@ class CONTENT_EXPORT InProcessChildThreadParams {
   }
 
  private:
-  std::string channel_name_;
   scoped_refptr<base::SequencedTaskRunner> io_runner_;
   std::string application_token_;
 };