Revert of Remove begin/end subseq. display items, and store on PaintController instead.

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

Index: third_party/WebKit/Source/platform/graphics/paint/PaintController.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/paint/PaintController.cpp b/third_party/WebKit/Source/platform/graphics/paint/PaintController.cpp
index ac49b8ada5618d180554bfaf35424a13018f422f..fa5209e751107c4f0f9f924bae93f7da4b670292 100644
--- a/third_party/WebKit/Source/platform/graphics/paint/PaintController.cpp
+++ b/third_party/WebKit/Source/platform/graphics/paint/PaintController.cpp
@@ -99,28 +99,22 @@
     return false;
   }
 
-  SubsequenceMarkers* markers = getSubsequenceMarkers(client);
-  if (!markers) {
+  size_t cachedItem =
+      findCachedItem(DisplayItem::Id(client, DisplayItem::kSubsequence));
+  if (cachedItem == kNotFound) {
+    NOTREACHED();
     return false;
   }
 
   // |cachedItem| will point to the first item after the subsequence or end of
   // the current list.
   ensureNewDisplayItemListInitialCapacity();
-
-  size_t sizeBeforeCopy = m_newDisplayItemList.size();
-  copyCachedSubsequence(markers->start, markers->end);
-
-  if (!RuntimeEnabledFeatures::paintUnderInvalidationCheckingEnabled()) {
-    addCachedSubsequence(client, sizeBeforeCopy,
-                         m_newDisplayItemList.size() - 1);
-  }
-
-  m_nextItemToMatch = markers->end + 1;
-  // Items before |m_nextItemToMatch| have been copied so we don't need to index
-  // them.
-  if (m_nextItemToMatch > m_nextItemToIndex)
-    m_nextItemToIndex = m_nextItemToMatch;
+  copyCachedSubsequence(cachedItem);
+
+  m_nextItemToMatch = cachedItem;
+  // Items before |cachedItem| have been copied so we don't need to index them.
+  if (cachedItem > m_nextItemToIndex)
+    m_nextItemToIndex = cachedItem;
 
   if (RuntimeEnabledFeatures::paintUnderInvalidationCheckingEnabled()) {
     // Return false to let the painter actually paint. We will check if the new
@@ -129,40 +123,6 @@
   }
 
   return true;
-}
-
-PaintController::SubsequenceMarkers* PaintController::getSubsequenceMarkers(
-    const DisplayItemClient& client) {
-  auto result = m_currentCachedSubsequences.find(&client);
-  if (result == m_currentCachedSubsequences.end())
-    return nullptr;
-  return &result->value;
-}
-
-void PaintController::addCachedSubsequence(const DisplayItemClient& client,
-                                           unsigned start,
-                                           unsigned end) {
-  DCHECK(start <= end);
-  DCHECK(end < m_newDisplayItemList.size());
-  if (isCheckingUnderInvalidation()) {
-    SubsequenceMarkers* markers = getSubsequenceMarkers(client);
-    if (!markers) {
-      showSequenceUnderInvalidationError(
-          "under-invalidation : unexpected subsequence", client, start, end);
-      DCHECK(false);
-    }
-    if (markers->end - markers->start != end - start) {
-      showSequenceUnderInvalidationError(
-          "under-invalidation: new subsequence wrong length", client, start,
-          end);
-      DCHECK(false);
-    }
-  }
-
-  DCHECK(m_newCachedSubsequences.find(&client) ==
-         m_newCachedSubsequences.end());
-
-  m_newCachedSubsequences.insert(&client, SubsequenceMarkers(start, end));
 }
 
 bool PaintController::lastDisplayItemIsNoopBegin() const {
@@ -210,29 +170,31 @@
   return nullptr;
 }
 
-#if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
-void PaintController::beginShouldKeepAlive(const DisplayItemClient& client) {
-  if (!isSkippingCache()) {
-    // Mark the client shouldKeepAlive under this PaintController.
-    // The status will end after the new display items are committed.
-    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.
-      client.beginShouldKeepAlive(m_currentSubsequenceClients.back());
-    }
-  }
-}
-#endif
-
 void PaintController::processNewItem(DisplayItem& displayItem) {
   DCHECK(!m_constructionDisabled);
 
 #if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
-  if (displayItem.isCacheable()) {
-    beginShouldKeepAlive(displayItem.client());
+  if (!isSkippingCache()) {
+    if (displayItem.isCacheable()) {
+      // 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.back());
+      }
+    }
+
+    if (displayItem.getType() == DisplayItem::kSubsequence) {
+      m_currentSubsequenceClients.push_back(&displayItem.client());
+    } else if (displayItem.getType() == DisplayItem::kEndSubsequence) {
+      CHECK(m_currentSubsequenceClients.back() == &displayItem.client());
+      m_currentSubsequenceClients.pop_back();
+    }
   }
 #endif
 
@@ -255,6 +217,7 @@
     const auto& beginDisplayItem =
         m_newDisplayItemList[m_newDisplayItemList.size() - 2];
     if (beginDisplayItem.isBegin() &&
+        beginDisplayItem.getType() != DisplayItem::kSubsequence &&
         !beginDisplayItem.drawsContent())
       DCHECK(!displayItem.isEndAndPairedWith(beginDisplayItem.getType()));
   }
@@ -430,29 +393,32 @@
   return kNotFound;
 }
 
-// Copies a cached subsequence from current list to the new list.
-// When paintUnderInvaldiationCheckingEnabled() we'll not actually
+// Copies a cached subsequence from current list to the new list. On return,
+// |cachedItemIndex| points to the item after the EndSubsequence item of the
+// subsequence. When paintUnderInvaldiationCheckingEnabled() we'll not actually
 // copy the subsequence, but mark the begin and end of the subsequence for
 // under-invalidation checking.
-void PaintController::copyCachedSubsequence(size_t beginIndex,
-                                            size_t endIndex) {
+void PaintController::copyCachedSubsequence(size_t& cachedItemIndex) {
   AutoReset<size_t> subsequenceBeginIndex(
       &m_currentCachedSubsequenceBeginIndexInNewList,
       m_newDisplayItemList.size());
   DisplayItem* cachedItem =
-      &m_currentPaintArtifact.getDisplayItemList()[beginIndex];
+      &m_currentPaintArtifact.getDisplayItemList()[cachedItemIndex];
+  DCHECK(cachedItem->getType() == DisplayItem::kSubsequence);
 
   if (RuntimeEnabledFeatures::paintUnderInvalidationCheckingEnabled()) {
     DCHECK(!isCheckingUnderInvalidation());
-    m_underInvalidationCheckingBegin = beginIndex;
+    m_underInvalidationCheckingBegin = cachedItemIndex;
     m_underInvalidationMessagePrefix =
         "(In cached subsequence of " + cachedItem->client().debugName() + ")";
   }
 
+  DisplayItem::Id endSubsequenceId(cachedItem->client(),
+                                   DisplayItem::kEndSubsequence);
   Vector<PaintChunk>::const_iterator cachedChunk;
   if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
     cachedChunk =
-        m_currentPaintArtifact.findChunkByDisplayItemIndex(beginIndex);
+        m_currentPaintArtifact.findChunkByDisplayItemIndex(cachedItemIndex);
     DCHECK(cachedChunk != m_currentPaintArtifact.paintChunks().end());
     updateCurrentPaintChunkProperties(
         cachedChunk->id ? &*cachedChunk->id : nullptr, cachedChunk->properties);
@@ -461,32 +427,40 @@
     cachedChunk = m_currentPaintArtifact.paintChunks().begin();
   }
 
-  for (size_t currentIndex = beginIndex; currentIndex <= endIndex;
-       ++currentIndex) {
-    cachedItem = &m_currentPaintArtifact.getDisplayItemList()[currentIndex];
+  while (true) {
     DCHECK(cachedItem->hasValidClient());
 #if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
     CHECK(cachedItem->client().isAlive());
 #endif
     ++m_numCachedNewItems;
+    bool metEndSubsequence = cachedItem->getId() == endSubsequenceId;
     if (!RuntimeEnabledFeatures::paintUnderInvalidationCheckingEnabled()) {
       if (RuntimeEnabledFeatures::slimmingPaintV2Enabled() &&
-          currentIndex == cachedChunk->endIndex) {
+          cachedItemIndex == cachedChunk->endIndex) {
         ++cachedChunk;
         DCHECK(cachedChunk != m_currentPaintArtifact.paintChunks().end());
         updateCurrentPaintChunkProperties(
             cachedChunk->id ? &*cachedChunk->id : nullptr,
             cachedChunk->properties);
       }
-      processNewItem(moveItemFromCurrentListToNewList(currentIndex));
+      processNewItem(moveItemFromCurrentListToNewList(cachedItemIndex));
       if (RuntimeEnabledFeatures::slimmingPaintV2Enabled())
         DCHECK((!m_newPaintChunks.lastChunk().id && !cachedChunk->id) ||
                m_newPaintChunks.lastChunk().matches(*cachedChunk));
     }
+
+    ++cachedItemIndex;
+    if (metEndSubsequence)
+      break;
+
+    // We should always be able to find the EndSubsequence display item.
+    DCHECK(cachedItemIndex <
+           m_currentPaintArtifact.getDisplayItemList().size());
+    cachedItem = &m_currentPaintArtifact.getDisplayItemList()[cachedItemIndex];
   }
 
   if (RuntimeEnabledFeatures::paintUnderInvalidationCheckingEnabled()) {
-    m_underInvalidationCheckingEnd = endIndex + 1;
+    m_underInvalidationCheckingEnd = cachedItemIndex;
     DCHECK(isCheckingUnderInvalidation());
   }
 }
@@ -518,6 +492,7 @@
                "num_non_cached_new_items",
                (int)m_newDisplayItemList.size() - m_numCachedNewItems);
   m_numCachedNewItems = 0;
+
   // These data structures are used during painting only.
   DCHECK(!isSkippingCache());
 #if DCHECK_IS_ON()
@@ -532,16 +507,6 @@
 
   m_currentCacheGeneration =
       DisplayItemClient::CacheGenerationOrInvalidationReason::next();
-
-  m_newCachedSubsequences.swap(m_currentCachedSubsequences);
-  m_newCachedSubsequences.clear();
-  for (auto& item : m_currentCachedSubsequences) {
-    item.key->setDisplayItemsCached(m_currentCacheGeneration);
-#if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
-    DisplayItemClient::endShouldKeepAliveAllClients(item.key);
-#endif
-  }
-
   Vector<const DisplayItemClient*> skippedCacheClients;
   for (const auto& item : m_newDisplayItemList) {
     // No reason to continue the analysis once we have a veto.
@@ -601,6 +566,7 @@
   m_newDisplayItemList = DisplayItemList(0);
 
 #if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
+  CHECK(m_currentSubsequenceClients.isEmpty());
   DisplayItemClient::endShouldKeepAliveAllClients(this);
 #endif
 
@@ -819,21 +785,6 @@
 #endif  // NDEBUG
 }
 
-void PaintController::showSequenceUnderInvalidationError(
-    const char* reason,
-    const DisplayItemClient& client,
-    int start,
-    int end) {
-  LOG(ERROR) << m_underInvalidationMessagePrefix << " " << reason;
-  LOG(ERROR) << "Subsequence client: " << client.debugName();
-#ifndef NDEBUG
-//  showDebugData();
-#else
-  LOG(ERROR) << "Run debug build to get more details.";
-#endif
-  LOG(ERROR) << "See http://crbug.com/619103.";
-}
-
 void PaintController::checkUnderInvalidation() {
   DCHECK(RuntimeEnabledFeatures::paintUnderInvalidationCheckingEnabled());