UMA histogram for longest renderer main thread usage for page save to MHTML.

content/browser/download/mhtml_generation_manager.cc

 // Copyright (c) 2012 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.
 
 #include "content/browser/download/mhtml_generation_manager.h"
 
 #include <map>
 #include <queue>
 #include <utility>
 
@@ skipping 88 matching lines @@
 
   // Id used to map renderer responses to jobs.
   // See also MHTMLGenerationManager::id_to_job_ map.
   const int job_id_;
 
   // Time tracking for performance metrics reporting.
   const base::TimeTicks creation_time_;
   base::TimeTicks wait_on_renderer_start_time_;
   base::TimeDelta all_renderers_wait_time_;
   base::TimeDelta all_renderers_main_thread_time_;
+  base::TimeDelta longest_renderer_main_thread_time_;
 
   // User-configurable parameters. Includes the file location, binary encoding
   // choices, and whether to skip storing resources marked
   // Cache-Control: no-store.
   MHTMLGenerationParams params_;
 
   // The IDs of frames that still need to be processed.
   std::queue<int> pending_frame_tree_node_ids_;
 
   // Identifies a frame to which we've sent FrameMsg_SerializeAsMHTML but for
@@ skipping 156 matching lines @@
     UMA_HISTOGRAM_TIMES(
         "PageSerialization.MhtmlGeneration.BrowserWaitForRendererTime."
         "FrameTree",
         all_renderers_wait_time_);
   }
   if (!all_renderers_main_thread_time_.is_zero()) {
     UMA_HISTOGRAM_TIMES(
         "PageSerialization.MhtmlGeneration.RendererMainThreadTime.FrameTree",
         all_renderers_main_thread_time_);
   }
+  if (!longest_renderer_main_thread_time_.is_zero()) {
+    UMA_HISTOGRAM_TIMES(
+        "PageSerialization.MhtmlGeneration.RendererMainThreadTime.SlowestFrame",
+        longest_renderer_main_thread_time_);
+  }
 
   // Stopping RenderProcessExited notifications is needed to avoid calling
   // JobFinished twice.  See also https://crbug.com/612098.
   observed_renderer_process_host_.RemoveAll();
 }
 
 void MHTMLGenerationManager::Job::ReportRendererMainThreadTime(
     base::TimeDelta renderer_main_thread_time) {
   DCHECK(renderer_main_thread_time > base::TimeDelta());
   if (renderer_main_thread_time > base::TimeDelta())
     all_renderers_main_thread_time_ += renderer_main_thread_time;
+  if (renderer_main_thread_time > longest_renderer_main_thread_time_)
+    longest_renderer_main_thread_time_ = renderer_main_thread_time;
 }
 
 void MHTMLGenerationManager::Job::AddFrame(RenderFrameHost* render_frame_host) {
   auto* rfhi = static_cast<RenderFrameHostImpl*>(render_frame_host);
   int frame_tree_node_id = rfhi->frame_tree_node()->frame_tree_node_id();
   pending_frame_tree_node_ids_.push(frame_tree_node_id);
 
   std::string guid = base::GenerateGUID();
   std::string content_id = base::StringPrintf("<frame-%d-%s@mhtml.blink>",
                                               frame_tree_node_id, guid.c_str());
@@ skipping 224 matching lines @@
   return iter->second;
 }
 
 void MHTMLGenerationManager::RenderProcessExited(Job* job) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   DCHECK(job);
   JobFinished(job, JobStatus::FAILURE);
 }
 
 }  // namespace content