Revert of memory-infra: Finish moving to Mojo (2nd attempt)

content/public/common/child_process_host.h

Index: content/public/common/child_process_host.h
diff --git a/content/public/common/child_process_host.h b/content/public/common/child_process_host.h
index 51e617f8e901715bf2709aeb954d70733ad5ebde..6a541cb1048a20e0611ecff1dada98a0d7b61b47 100644
--- a/content/public/common/child_process_host.h
+++ b/content/public/common/child_process_host.h
@@ -39,6 +39,11 @@
   // This is a value never returned as the unique id of any child processes of
   // any kind, including the values returned by RenderProcessHost::GetID().
   static int kInvalidUniqueID;
+
+  // This value is used as the tracing id of the browser process for identifying
+  // cross-process shared memory segments when tracing.
+  // Note: In single-process mode all the clients of tracing will use this id.
+  static uint64_t kBrowserTracingProcessId;
 
   // Used to create a child process host. The delegate must outlive this object.
   static ChildProcessHost* Create(ChildProcessHostDelegate* delegate);