Check DisplayItemCient aliveness in cached subsequences

third_party/WebKit/Source/platform/graphics/paint/PaintController.cpp

 // 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.
 
 #include "platform/graphics/paint/PaintController.h"
 
 #include "platform/TraceEvent.h"
 #include "platform/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/DrawingDisplayItem.h"
 #include "third_party/skia/include/core/SkPictureAnalyzer.h"
@@ skipping 48 matching lines @@
     if (RuntimeEnabledFeatures::slimmingPaintV2Enabled())
         m_newPaintChunks.decrementDisplayItemIndex();
 }
 
 void PaintController::processNewItem(DisplayItem& displayItem)
 {
     DCHECK(!m_constructionDisabled);
     DCHECK(!skippingCache() || !displayItem.isCached());
 
 #if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
-    if (!skippingCache() && (displayItem.isCacheable() || displayItem.isCached()))
-        displayItem.client().beginShouldKeepAlive(this);
+    if (!skippingCache()) {
+        if (displayItem.isCacheable() || displayItem.isCached()) {
+            // Mark the client shouldKeepAlive under this PaintController.
+            // The status will end after the new display items are committed.
+            displayItem.client().beginShouldKeepAlive(this);
+
+            if (!m_currentSubsequenceClients.isEmpty()) {
+                // Mark the client shouldKeepAlive under the current subsequence.
+                // The status will end when the subsequence owner is invalidated or deleted.
+                displayItem.client().beginShouldKeepAlive(m_currentSubsequenceClients.last());
+            }
+        }
+
+        if (displayItem.getType() == DisplayItem::Subsequence) {
+            m_currentSubsequenceClients.append(&displayItem.client());
+        } else if (displayItem.getType() == DisplayItem::EndSubsequence) {
+            CHECK(m_currentSubsequenceClients.last() == &displayItem.client());
+            m_currentSubsequenceClients.removeLast();
+        }
+    }
 #endif
 
     if (displayItem.isCached())
         ++m_numCachedNewItems;
 
 #if DCHECK_IS_ON()
     // Verify noop begin/end pairs have been removed.
     if (m_newDisplayItemList.size() >= 2 && displayItem.isEnd()) {
         const auto& beginDisplayItem = m_newDisplayItemList[m_newDisplayItemList.size() - 2];
         if (beginDisplayItem.isBegin() && beginDisplayItem.getType() != DisplayItem::Subsequence && !beginDisplayItem.drawsContent())
@@ skipping 315 matching lines @@
 
 void PaintController::updateCacheGeneration()
 {
     m_currentCacheGeneration = DisplayItemCacheGeneration::next();
     for (const DisplayItem& displayItem : m_currentPaintArtifact.getDisplayItemList()) {
         if (!displayItem.isCacheable())
             continue;
         displayItem.client().setDisplayItemsCached(m_currentCacheGeneration);
     }
 #if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
+    CHECK(m_currentSubsequenceClients.isEmpty());
     DisplayItemClient::endShouldKeepAliveAllClients(this);
 #endif
 }
 
 void PaintController::appendDebugDrawingAfterCommit(const DisplayItemClient& displayItemClient, PassRefPtr<SkPicture> picture, const LayoutSize& offsetFromLayoutObject)
 {
     DCHECK(m_newDisplayItemList.isEmpty());
     DrawingDisplayItem& displayItem = m_currentPaintArtifact.getDisplayItemList().allocateAndConstruct<DrawingDisplayItem>(displayItemClient, DisplayItem::DebugDrawing, picture);
     displayItem.setSkippedCache();
     m_currentPaintArtifact.getDisplayItemList().appendVisualRect(visualRectForDisplayItem(displayItem, offsetFromLayoutObject));
@@ skipping 111 matching lines @@
 
 void PaintController::showDebugData() const
 {
     WTFLogAlways("current display item list: [%s]\n", displayItemListAsDebugString(m_currentPaintArtifact.getDisplayItemList()).utf8().data());
     WTFLogAlways("new display item list: [%s]\n", displayItemListAsDebugString(m_newDisplayItemList).utf8().data());
 }
 
 #endif // ifndef NDEBUG
 
 } // namespace blink