Changes PlzNavitate histograms to try and simplify their multi-modal characteristic.

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 978916c009d46101ba764c358630c24d8b93f6eb..a441e7d21a37cbfcaed664b89d251f50ed567111 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -643,6 +643,7 @@ bool RenderProcessHostImpl::Init() {
   power_monitor_broadcaster_.Init();
 
   is_initialized_ = true;
+  init_time_ = base::TimeTicks::Now();

[nasko, 2014/10/13 15:55:24]

This is the time we call Init. This is not the time that the process is created,
which is later in time. Does it make a difference in this case?

[carlosk, 2014/10/13 18:01:46]

It does not make a difference. I updated its getter comment to better explain
what it is.

   return true;
 }
 
@@ -920,6 +921,10 @@ ServiceRegistry* RenderProcessHostImpl::GetServiceRegistry() {
   return mojo_application_host_->service_registry();
 }
 
+const base::TimeTicks& RenderProcessHostImpl::GetInitTime() const {
+  return init_time_;
+}
+
 void RenderProcessHostImpl::AddRoute(
     int32 routing_id,
     IPC::Listener* listener) {