Remove RenderWidgetHostLatencyTracker::OnSwapCompositorFrame

This method adds the right component id to snapshot-related latency
info, We can just send the right component id to the renderer so that
a correction browser-side is not necessary.

Test: Lots of pixel tests take screenshots. Also tested
Page.captureScreenshot manually.

Bug: 810037, 775030
Change-Id: I61242ad63c5af8975331cb405fc629ce19ef92f8
Reviewed-on: https://chromium-review.googlesource.com/1019389
Commit-Queue: Saman Sami <samans@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#552204}

content/browser/renderer_host/input/render_widget_host_latency_tracker.cc

@@ -33,37 +33,6 @@ ukm::SourceId GenerateUkmSourceId() {
   return ukm_recorder ? ukm_recorder->GetNewSourceID() : ukm::kInvalidSourceId;
 }
 
-// LatencyComponents generated in the renderer must have component IDs
-// provided to them by the browser process. This function adds the correct
-// component ID where necessary.
-void AddLatencyInfoComponentIds(LatencyInfo* latency,
-                                int64_t latency_component_id) {
-  std::vector<std::pair<ui::LatencyComponentType, int64_t>> new_components_key;
-  std::vector<LatencyInfo::LatencyComponent> new_components_value;
-  for (const auto& lc : latency->latency_components()) {
-    ui::LatencyComponentType component_type = lc.first.first;
-    if (component_type == ui::BROWSER_SNAPSHOT_FRAME_NUMBER_COMPONENT) {
-      // Generate a new component entry with the correct component ID
-      new_components_key.push_back(std::make_pair(component_type,
-                                                  latency_component_id));
-      new_components_value.push_back(lc.second);
-    }
-  }
-
-  // Remove the entries with invalid component IDs.
-  latency->RemoveLatency(ui::BROWSER_SNAPSHOT_FRAME_NUMBER_COMPONENT);
-
-  // Add newly generated components into the latency info
-  for (size_t i = 0; i < new_components_key.size(); i++) {
-    latency->AddLatencyNumberWithTimestamp(
-        new_components_key[i].first,
-        new_components_key[i].second,
-        new_components_value[i].sequence_number,
-        new_components_value[i].event_time,
-        new_components_value[i].event_count);
-  }
-}
-
 void RecordEQTAccuracy(base::TimeDelta queueing_time,
                        base::TimeDelta expected_queueing_time) {
   float queueing_time_ms = queueing_time.InMillisecondsF();
@@ -336,12 +305,4 @@ void RenderWidgetHostLatencyTracker::OnInputEventAck(
                                 *latency, ack_result);
 }
 
-void RenderWidgetHostLatencyTracker::OnSwapCompositorFrame(
-    std::vector<LatencyInfo>* latencies) {
-  DCHECK(latencies);
-  for (LatencyInfo& latency : *latencies) {
-    AddLatencyInfoComponentIds(&latency, latency_component_id_);
-  }
-}
-
 }  // namespace content

content/browser/renderer_host/input/render_widget_host_latency_tracker.h

@@ -52,11 +52,6 @@ class CONTENT_EXPORT RenderWidgetHostLatencyTracker
                        ui::LatencyInfo* latency,
                        InputEventAckState ack_result);
 
-  // Populates renderer-created LatencyInfo entries with the appropriate latency
-  // component id. Called when the RenderWidgetHost receives a compositor swap
-  // update from the renderer.
-  void OnSwapCompositorFrame(std::vector<ui::LatencyInfo>* latencies);
-
   void reset_delegate() { render_widget_host_delegate_ = nullptr; }
 
   // Returns the ID that uniquely describes this component to the latency

content/browser/renderer_host/render_widget_host_impl.cc

@@ -1705,7 +1705,7 @@ void RenderWidgetHostImpl::GetSnapshotFromBrowser(
     pending_surface_browser_snapshots_.insert(std::make_pair(id, callback));
     ui::LatencyInfo latency_info;
     latency_info.AddLatencyNumber(ui::BROWSER_SNAPSHOT_FRAME_NUMBER_COMPONENT,
-                                  0, id);
+                                  GetLatencyComponentId(), id);
     Send(new ViewMsg_ForceRedraw(GetRoutingID(), latency_info));
     return;
   }
@@ -1719,8 +1719,8 @@ void RenderWidgetHostImpl::GetSnapshotFromBrowser(
 #endif
   pending_browser_snapshots_.insert(std::make_pair(id, callback));
   ui::LatencyInfo latency_info;
-  latency_info.AddLatencyNumber(ui::BROWSER_SNAPSHOT_FRAME_NUMBER_COMPONENT, 0,
-                                id);
+  latency_info.AddLatencyNumber(ui::BROWSER_SNAPSHOT_FRAME_NUMBER_COMPONENT,
+                                GetLatencyComponentId(), id);
   Send(new ViewMsg_ForceRedraw(GetRoutingID(), latency_info));
 }
 
@@ -2020,6 +2020,9 @@ void RenderWidgetHostImpl::ClearDisplayedGraphics() {
 
 void RenderWidgetHostImpl::OnGpuSwapBuffersCompletedInternal(
     const ui::LatencyInfo& latency_info) {
+  // Note that a compromised renderer can send LatencyInfo to a
+  // RenderWidgetHostImpl other than its own. Be mindful of security
+  // implications of the code you add here.
   ui::LatencyInfo::LatencyComponent window_snapshot_component;
   if (latency_info.FindLatency(ui::BROWSER_SNAPSHOT_FRAME_NUMBER_COMPONENT,
                                GetLatencyComponentId(),
@@ -2967,8 +2970,6 @@ void RenderWidgetHostImpl::SubmitCompositorFrame(
 
   last_frame_metadata_ = frame.metadata.Clone();
 
-  latency_tracker_.OnSwapCompositorFrame(&frame.metadata.latency_info);
-
   bool is_mobile_optimized = IsMobileOptimizedFrame(frame.metadata);
   input_router_->NotifySiteIsMobileOptimized(is_mobile_optimized);
   if (touch_emulator_)