Move inspector layer view update after LayerTreeHost::UpdateLayers

The inspector uses layer and cc property tree information to update the
layer view via LayerTreeDidChange. Previously, this was called after
paint but before the property trees had updated to-screen transforms
(calculated in draw_property_utils::UpdatePropertyTrees) which resulted
in incorrect layer positions. This patch moves the LayerTreeDidChange
notification after LayerTreeHost::UpdateLayers which is the first point
where cc property trees have correct to-screen transforms. This fixes
the inspector layer positioning.

Bug: 977578
Change-Id: Ie033508eb2985b3bce8c8494558a4788b9c65fa2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1726874
Commit-Queue: Philip Rogers <pdr@chromium.org>
Reviewed-by: Chris Harrelson OOO <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685866}

third_party/blink/renderer/core/exported/web_view_impl.cc

@@ -143,6 +143,7 @@
 #include "third_party/blink/renderer/core/paint/first_meaningful_paint_detector.h"
 #include "third_party/blink/renderer/core/paint/paint_layer_scrollable_area.h"
 #include "third_party/blink/renderer/core/paint/paint_timing_detector.h"
+#include "third_party/blink/renderer/core/probe/core_probes.h"
 #include "third_party/blink/renderer/core/scroll/scrollbar_theme.h"
 #include "third_party/blink/renderer/core/timing/dom_window_performance.h"
 #include "third_party/blink/renderer/core/timing/window_performance.h"
@@ -1534,6 +1535,8 @@ void WebViewImpl::EndUpdateLayers() {
     MainFrameImpl()->GetFrame()->View()->EnsureUkmAggregator().RecordSample(
         LocalFrameUkmAggregator::kUpdateLayers,
         update_layers_start_time_.value(), base::TimeTicks::Now());
+    if (RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled())
+      probe::LayerTreeDidChange(MainFrameImpl()->GetFrame());
   }
   update_layers_start_time_.reset();
 }

third_party/blink/renderer/core/frame/web_frame_widget_impl.cc

@@ -81,6 +81,7 @@
 #include "third_party/blink/renderer/core/page/pointer_lock_controller.h"
 #include "third_party/blink/renderer/core/page/validation_message_client.h"
 #include "third_party/blink/renderer/core/paint/compositing/paint_layer_compositor.h"
+#include "third_party/blink/renderer/core/probe/core_probes.h"
 #include "third_party/blink/renderer/platform/graphics/color.h"
 #include "third_party/blink/renderer/platform/keyboard_codes.h"
 
@@ -317,6 +318,8 @@ void WebFrameWidgetImpl::EndUpdateLayers() {
     LocalRootImpl()->GetFrame()->View()->EnsureUkmAggregator().RecordSample(
         LocalFrameUkmAggregator::kUpdateLayers,
         update_layers_start_time_.value(), base::TimeTicks::Now());
+    if (RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled())
+      probe::LayerTreeDidChange(LocalRootImpl()->GetFrame());
   }
   update_layers_start_time_.reset();
 }

third_party/blink/renderer/core/inspector/inspector_layer_tree_agent.cc

@@ -274,8 +274,10 @@ Response InspectorLayerTreeAgent::enable() {
 
   if (RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled() ||
       RuntimeEnabledFeatures::CompositeAfterPaintEnabled()) {
-    if (document->Lifecycle().GetState() >= DocumentLifecycle::kPaintClean)
+    if (document->Lifecycle().GetState() >= DocumentLifecycle::kPaintClean) {
       LayerTreePainted();
+      LayerTreeDidChange();
+    }
   } else if (document->Lifecycle().GetState() >=
              DocumentLifecycle::kCompositingClean) {
     LayerTreeDidChange();
@@ -290,8 +292,6 @@ Response InspectorLayerTreeAgent::disable() {
 }
 
 void InspectorLayerTreeAgent::LayerTreeDidChange() {
-  DCHECK(!RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled() &&
-         !RuntimeEnabledFeatures::CompositeAfterPaintEnabled());
   GetFrontend()->layerTreeDidChange(BuildLayerTree());
 }
 
@@ -320,8 +320,6 @@ void InspectorLayerTreeAgent::LayerTreePainted() {
   DCHECK(RuntimeEnabledFeatures::BlinkGenPropertyTreesEnabled() ||
          RuntimeEnabledFeatures::CompositeAfterPaintEnabled());
 
-  GetFrontend()->layerTreeDidChange(BuildLayerTree());
-
   for (const auto& layer :
        inspected_frames_->Root()->View()->RootCcLayer()->children()) {
     if (!layer->update_rect().IsEmpty()) {

third_party/blink/web_tests/http/tests/devtools/layers/layers-3d-view-after-update-expected.txt

@@ -0,0 +1,4 @@
+Layers after update in Layers3DView
+
+Pass: Layer quads are unchanged by no-op update
+

third_party/blink/web_tests/http/tests/devtools/layers/layers-3d-view-after-update.js

@@ -0,0 +1,41 @@
+// Copyright 2019 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.
+
+(async function() {
+  TestRunner.addResult(`Layers after update in Layers3DView\n`);
+  await TestRunner.loadModule('layers_test_runner');
+
+  await TestRunner.loadHTML(`
+      <style>
+        #layer {
+          will-change: transform;
+          width: 300px;
+          height: 300px;
+          transform: translate(100px, 100px);
+        }
+      </style>
+      <div id="layer"></div>
+  `);
+
+  TestRunner.showPanel('layers');
+  await LayersTestRunner.requestLayers();
+  var layer = LayersTestRunner.findLayerByNodeIdAttribute('layer');
+  initialQuads = layer.quad().toString();
+
+  // Updating layers should not produce invalid layer to-screen transforms
+  // (see: https://crbug.com/977578). Backface visibility is changed, rather
+  // than just adjusting the transform, to ensure fast-path optimizations do not
+  // prevent a full layer tree update.
+  await LayersTestRunner.evaluateAndWaitForTreeChange(
+      'layer.style.backfaceVisibility = "hidden";');
+
+  layer = LayersTestRunner.findLayerByNodeIdAttribute('layer');
+  if (initialQuads === layer.quad().toString())
+    TestRunner.addResult('Pass: Layer quads are unchanged by no-op update');
+  else
+    TestRunner.addResult('Fail: Layer quads are changed by no-op update');
+
+  TestRunner.completeTest();
+})();
+