Buffer cross frame paint timing updates.

chrome/browser/page_load_metrics/page_load_metrics_update_dispatcher.h

 // Copyright 2017 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.
 
 #ifndef CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_UPDATE_DISPATCHER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_UPDATE_DISPATCHER_H_
 
 #include <map>
 
 #include "base/macros.h"
 #include "base/time/time.h"
+#include "base/timer/timer.h"

[Charlie Harrison, 2017/05/26 19:31:34]

Can just fwd declare I think

[Bryan McQuade, 2017/05/26 20:07:32]

Done

 #include "chrome/common/page_load_metrics/page_load_metrics.mojom.h"
 
 namespace content {
 class NavigationHandle;
 class RenderFrameHost;
 }  // namespace content
 
 namespace page_load_metrics {
 
 class PageLoadMetricsEmbedderInterface;
@@ skipping 36 matching lines @@
   INVALID_ORDER_FIRST_PAINT_FIRST_TEXT_PAINT,
   INVALID_ORDER_FIRST_PAINT_FIRST_IMAGE_PAINT,
   INVALID_ORDER_FIRST_PAINT_FIRST_CONTENTFUL_PAINT,
   INVALID_ORDER_FIRST_PAINT_FIRST_MEANINGFUL_PAINT,
 
   // New values should be added before this final entry.
   LAST_PAGE_LOAD_TIMING_STATUS
 };
 
 extern const char kPageLoadTimingStatus[];
+extern const char kHistogramOutOfOrderTiming[];
+extern const char kHistogramOutOfOrderTimingBuffered[];
 
 }  // namespace internal
 
 // PageLoadMetricsUpdateDispatcher manages updates to page load metrics data,
 // and dispatches them to the Client. PageLoadMetricsUpdateDispatcher may delay
 // dispatching metrics updates to the Client in cases where metrics state hasn't
 // stabilized.
 class PageLoadMetricsUpdateDispatcher {
  public:
   // The Client class is updated when metrics managed by the dispatcher have
@@ skipping 37 matching lines @@
  private:
   using FrameTreeNodeId = int;
 
   void UpdateMainFrameTiming(const mojom::PageLoadTiming& new_timing);
   void UpdateSubFrameTiming(content::RenderFrameHost* render_frame_host,
                             const mojom::PageLoadTiming& new_timing);
 
   void UpdateMainFrameMetadata(const mojom::PageLoadMetadata& new_metadata);
   void UpdateSubFrameMetadata(const mojom::PageLoadMetadata& subframe_metadata);
 
-  // Merge values from |new_paint_timing| into |pending_merged_page_timing_|,
-  // offsetting any new timings by the |navigation_start_offset|.
-  void MergePaintTiming(base::TimeDelta navigation_start_offset,
-                        const mojom::PaintTiming& new_paint_timing,
-                        bool is_main_frame);
-
+  void MaybeDispatchTimingUpdates(bool did_merge_new_timing_value);
   void DispatchTimingUpdates();
 
   // The client is guaranteed to outlive this object.
   Client* const client_;
 
   // Interface to chrome features. Must outlive the class.
   PageLoadMetricsEmbedderInterface* const embedder_interface_;
 
+  std::unique_ptr<base::Timer> timer_;
+
   // Time the navigation for this page load was initiated.
   const base::TimeTicks navigation_start_;
 
   // PageLoadTiming for the currently tracked page. The fields in |paint_timing|
   // are merged across all frames in the document. All other fields are from the
   // main frame document. |current_merged_page_timing_| contains the most recent
   // valid page load timing data, while pending_merged_page_timing_ contains
   // pending updates received since |current_merged_page_timing_| was last
   // dispatched to the client. pending_merged_page_timing_ will be copied to
   // |current_merged_page_timing_| once it is valid, at the time the
   // Client::OnTimingChanged callback is invoked.
   mojom::PageLoadTimingPtr current_merged_page_timing_;
   mojom::PageLoadTimingPtr pending_merged_page_timing_;
 
   mojom::PageLoadMetadataPtr main_frame_metadata_;
   mojom::PageLoadMetadataPtr subframe_metadata_;
 
   // Navigation start offsets for the most recently committed document in each
   // frame.
   std::map<FrameTreeNodeId, base::TimeDelta> subframe_navigation_start_offset_;
 
   DISALLOW_COPY_AND_ASSIGN(PageLoadMetricsUpdateDispatcher);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_UPDATE_DISPATCHER_H_