Always report maybe-clipped when painting fragmented content

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/graphics/GraphicsLayer.h"
 #include "platform/graphics/paint/DrawingDisplayItem.h"
 #include "platform/instrumentation/tracing/TraceEvent.h"
 #include "platform/wtf/AutoReset.h"
@@ skipping 436 matching lines @@
   AutoReset<size_t> subsequence_begin_index(
       &current_cached_subsequence_begin_index_in_new_list_,
       new_display_item_list_.size());
   DisplayItem* cached_item =
       &current_paint_artifact_.GetDisplayItemList()[begin_index];
 
   if (RuntimeEnabledFeatures::paintUnderInvalidationCheckingEnabled()) {
     DCHECK(!IsCheckingUnderInvalidation());
     under_invalidation_checking_begin_ = begin_index;
     under_invalidation_message_prefix_ =
-        "(In cached subsequence of " + cached_item->Client().DebugName() + ")";
+        "(In cached subsequence starting with " +
+        cached_item->Client().DebugName() + ")";
   }
 
   Vector<PaintChunk>::const_iterator cached_chunk;
   if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
     cached_chunk =
         current_paint_artifact_.FindChunkByDisplayItemIndex(begin_index);
     DCHECK(cached_chunk != current_paint_artifact_.PaintChunks().end());
     UpdateCurrentPaintChunkProperties(
         cached_chunk->id ? &*cached_chunk->id : nullptr,
         cached_chunk->properties);
@@ skipping 401 matching lines @@
           : nullptr;
 
   bool old_and_new_equal = old_item && new_item.Equals(*old_item);
   if (!old_and_new_equal) {
     if (new_item.IsBegin()) {
       // Temporarily skip mismatching begin display item which may be removed
       // when we remove a no-op pair.
       ++skipped_probable_under_invalidation_count_;
       return;
     }
-    if (new_item.IsDrawing() &&
-        skipped_probable_under_invalidation_count_ == 1) {
-      DCHECK_GE(new_display_item_list_.size(), 2u);
-      if (new_display_item_list_[new_display_item_list_.size() - 2].GetType() ==
-          DisplayItem::kBeginCompositing) {
-        // This might be a drawing item between a pair of begin/end compositing
-        // display items that will be folded into a single drawing display item.
-        ++skipped_probable_under_invalidation_count_;

[Xianzhu, 2017/04/18 00:15:21]

Doesn't the logic apply now?

[chrishtr, 2017/04/18 21:13:13]

It doesn't, because the folding optimization in CompositingRecorder is now gone,
right?

However, that CL was reverted again yesterday, so re-adding this code for now.

-        return;
-      }
-    }
   }
 
   if (skipped_probable_under_invalidation_count_ || !old_and_new_equal) {
     // If we ever skipped reporting any under-invalidations, report the earliest
     // one.
     ShowUnderInvalidationError(
         "under-invalidation: display item changed",
         new_display_item_list_[new_display_item_list_.size() -
                                skipped_probable_under_invalidation_count_ - 1],
         &current_paint_artifact_
@@ skipping 34 matching lines @@
               show_paint_records
                   ? (DisplayItemList::JsonOptions::kShowPaintRecords |
                      DisplayItemList::JsonOptions::kShowClientDebugName)
                   : DisplayItemList::JsonOptions::kShowClientDebugName)
           ->ToPrettyJSONString()
           .Utf8()
           .Data());
 }
 
 }  // namespace blink