Add histogram for how tab closing time. Did some cleanup along the way.

chrome/browser/renderer_host/render_view_host.cc

Index: chrome/browser/renderer_host/render_view_host.cc
===================================================================
--- chrome/browser/renderer_host/render_view_host.cc	(revision 28997)
+++ chrome/browser/renderer_host/render_view_host.cc	(working copy)
@@ -113,7 +113,6 @@
       navigations_suspended_(false),
       suspended_nav_message_(NULL),
       run_modal_reply_msg_(NULL),
-      is_showing_before_unload_dialog_(false),
       is_waiting_for_unload_ack_(false),
       unload_ack_is_for_cross_site_transition_(false),
       are_javascript_messages_suppressed_(false),
@@ -263,7 +262,7 @@
     // WebKit doesn't send throb notifications for JavaScript URLs, so we
     // don't want to either.
     if (!params.url.SchemeIs(chrome::kJavaScriptScheme))
-      delegate_->DidStartLoading(this);
+      delegate_->DidStartLoading();
   }
 }
 
@@ -587,13 +586,6 @@
     StartHangMonitorTimeout(TimeDelta::FromMilliseconds(kUnloadTimeoutMS));
   }
 
-  if (is_showing_before_unload_dialog_ && !success) {
-    // If a beforeunload dialog is canceled, we need to stop the throbber from
-    // spinning, since we forced it to start spinning in Navigate.
-    delegate_->DidStopLoading(this);
-  }
-  is_showing_before_unload_dialog_ = false;
-
   ViewHostMsg_RunJavaScriptMessage::WriteReplyParams(reply_msg,
                                                      success, prompt);
   Send(reply_msg);
@@ -1026,11 +1018,11 @@
 }
 
 void RenderViewHost::OnMsgDidStartLoading() {
-  delegate_->DidStartLoading(this);
+  delegate_->DidStartLoading();
 }
 
 void RenderViewHost::OnMsgDidStopLoading() {
-  delegate_->DidStopLoading(this);
+  delegate_->DidStopLoading();
 }
 
 void RenderViewHost::OnMsgDocumentAvailableInMainFrame() {
@@ -1336,7 +1328,6 @@
   // shouldn't process input events.
   process()->set_ignore_input_events(true);
   StopHangMonitorTimeout();
-  is_showing_before_unload_dialog_ = true;
   delegate_->RunBeforeUnloadConfirm(message, reply_msg);
 }