Fix FirstWebContentsProfiler not getting created when using session restore.

chrome/browser/metrics/first_web_contents_profiler.cc

 // Copyright 2014 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.
 
 #if !defined(OS_ANDROID)
 
 #include "chrome/browser/metrics/first_web_contents_profiler.h"
 
 #include <string>
 
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "components/metrics/profiler/tracking_synchronizer.h"
 #include "components/metrics/proto/profiler_event.pb.h"
 #include "components/startup_metric_utils/browser/startup_metric_utils.h"
 #include "content/public/browser/navigation_handle.h"
 
+void FirstWebContentsProfiler::WebContentsStarted(
+    content::WebContents* web_contents) {
+  static bool first_web_contents_profiled = false;
+  if (first_web_contents_profiled)
+    return;
+
+  first_web_contents_profiled = true;
+  new FirstWebContentsProfiler(web_contents);

[gab, 2016/10/04 19:15:17]

// FirstWebContentsProfiler owns itself.

[jam, 2016/10/04 19:19:17]

acknowledged, although in this case I think if someone cares knowing ownership
they can easily look at the source. (i.e. i view these kind of comments as
documenting what's obvious)

[gab, 2016/10/04 19:26:23]

okay, I personally find bare "new" surprising and thus like an explicit comment
telling the reader that this was intentional without having to dig further.

+}
+
 FirstWebContentsProfiler::FirstWebContentsProfiler(
     content::WebContents* web_contents)
     : content::WebContentsObserver(web_contents),
       collected_paint_metric_(false),
       collected_load_metric_(false),
       collected_main_navigation_start_metric_(false),
       collected_main_navigation_finished_metric_(false) {}
 
 void FirstWebContentsProfiler::DidFirstVisuallyNonEmptyPaint() {
   if (collected_paint_metric_)
@@ skipping 107 matching lines @@
   }
   if (!collected_load_metric_) {
     UMA_HISTOGRAM_ENUMERATION("Startup.FirstWebContents.FinishReason_NoLoad",
                               finish_reason, FinishReason::ENUM_MAX);
   }
 
   delete this;
 }
 
 #endif  // !defined(OS_ANDROID)