Show debug information for invalid display items

This may be helpful when we call showDebugData() during the merge
algorithm.

Review URL: https://codereview.chromium.org/1323263002

git-svn-id: svn://svn.chromium.org/blink/trunk@201817 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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

@@ -203,8 +203,6 @@ WTF::String DisplayItem::typeAsDebugString(Type type)
 
 WTF::String DisplayItem::asDebugString() const
 {
-    if (!isValid())
-        return "null";
     WTF::StringBuilder stringBuilder;
     stringBuilder.append('{');
     dumpPropertiesAsDebugString(stringBuilder);
@@ -214,7 +212,13 @@ WTF::String DisplayItem::asDebugString() const
 
 void DisplayItem::dumpPropertiesAsDebugString(WTF::StringBuilder& stringBuilder) const
 {
-    ASSERT(isValid());
+    if (!isValid()) {
+        stringBuilder.append("valid: false, originalDebugString: ");
+        // This is the original debug string which is in json format.
+        stringBuilder.append(clientDebugString());
+        return;
+    }
+
     stringBuilder.append(String::format("client: \"%p", client()));
     if (!clientDebugString().isEmpty()) {
         stringBuilder.append(' ');

third_party/WebKit/Source/platform/graphics/paint/DisplayItem.h

@@ -328,6 +328,7 @@ public:
 #ifndef NDEBUG
     static WTF::String typeAsDebugString(DisplayItem::Type);
     const WTF::String& clientDebugString() const { return m_clientDebugString; }
+    void setClientDebugString(const WTF::String& s) { m_clientDebugString = s; }
     WTF::String asDebugString() const;
     virtual void dumpPropertiesAsDebugString(WTF::StringBuilder&) const;
 #endif
@@ -344,9 +345,6 @@ private:
         , m_type(UninitializedType)
         , m_derivedSize(sizeof(*this))
         , m_skippedCache(false)
-#ifndef NDEBUG
-        , m_clientDebugString("invalid")
-#endif
     { }
 
     DisplayItemClient m_client;

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

@@ -281,7 +281,7 @@ void DisplayItemList::copyCachedSubsequence(DisplayItems::iterator& currentIt, D
     do {
         // We should always find the EndSubsequence display item.
         ASSERT(currentIt != m_currentDisplayItems.end());
-        updatedList.appendByMoving(*currentIt, currentIt->derivedSize());
+        updatedList.appendByMoving(*currentIt);
         ++currentIt;
     } while (!endSubsequenceId.matches(updatedList.last()));
 }
@@ -346,9 +346,7 @@ void DisplayItemList::commitNewDisplayItems(DisplayListDiff*)
 #endif // ENABLE(ASSERT)
 
     // TODO(jbroman): Consider revisiting this heuristic.
-    DisplayItems updatedList(
-        kMaximumDisplayItemSize,
-        std::max(m_currentDisplayItems.usedCapacityInBytes(), m_newDisplayItems.usedCapacityInBytes()));
+    DisplayItems updatedList(std::max(m_currentDisplayItems.usedCapacityInBytes(), m_newDisplayItems.usedCapacityInBytes()));
     DisplayItems::iterator currentIt = m_currentDisplayItems.begin();
     DisplayItems::iterator currentEnd = m_currentDisplayItems.end();
     for (DisplayItems::iterator newIt = m_newDisplayItems.begin(); newIt != m_newDisplayItems.end(); ++newIt) {
@@ -379,7 +377,7 @@ void DisplayItemList::commitNewDisplayItems(DisplayListDiff*)
             }
 
             if (newDisplayItem.isCachedDrawing()) {
-                updatedList.appendByMoving(*currentIt, currentIt->derivedSize());
+                updatedList.appendByMoving(*currentIt);
                 ++currentIt;
             } else {
                 ASSERT(newDisplayItem.type() == DisplayItem::CachedSubsequence);
@@ -397,7 +395,7 @@ void DisplayItemList::commitNewDisplayItems(DisplayListDiff*)
                     || (RuntimeEnabledFeatures::slimmingPaintV2Enabled() && paintOffsetWasInvalidated(newDisplayItem.client())));
             }
 #endif
-            updatedList.appendByMoving(*newIt, newIt->derivedSize());
+            updatedList.appendByMoving(*newIt);
 
             if (isSynchronized)
                 ++currentIt;
@@ -601,14 +599,12 @@ WTF::String DisplayItemList::displayItemsAsDebugString(const DisplayItems& list)
         const DisplayItem& displayItem = *it;
         if (i)
             stringBuilder.append(",\n");
-        if (!displayItem.isValid()) {
-            stringBuilder.append("null");
-            continue;
-        }
         stringBuilder.append(String::format("{index: %d, ", (int)i));
         displayItem.dumpPropertiesAsDebugString(stringBuilder);
+        if (displayItem.isValid()) {
             stringBuilder.append(", cacheIsValid: ");
             stringBuilder.append(clientCacheIsValid(displayItem.client()) ? "true" : "false");
+        }
         stringBuilder.append('}');
     }
     return stringBuilder.toString();

third_party/WebKit/Source/platform/graphics/paint/DisplayItemList.h

@@ -33,7 +33,26 @@ static const size_t kMaximumDisplayItemSize = sizeof(BeginTransform3DDisplayItem
 // which were invalidated on this frame and do not change SimpleLayers.
 using DisplayListDiff = HashMap<DisplayItemClient, DisplayItem*>;
 
-using DisplayItems = ContiguousContainer<DisplayItem, kDisplayItemAlignment>;
+class DisplayItems : public ContiguousContainer<DisplayItem, kDisplayItemAlignment> {
+public:
+    DisplayItems(size_t initialSizeBytes)
+        : ContiguousContainer(kMaximumDisplayItemSize, initialSizeBytes) {}
+
+    DisplayItem& appendByMoving(DisplayItem& item)
+    {
+#ifndef NDEBUG
+        WTF::String originalDebugString = item.asDebugString();
+#endif
+        DisplayItem& result = ContiguousContainer::appendByMoving(item, item.derivedSize());
+        // ContiguousContainer::appendByMoving() called in-place constructor on item, which invalidated it.
+        ASSERT(!item.isValid());
+#ifndef NDEBUG
+        // Save original debug string in the old item to help debugging.
+        item.setClientDebugString(originalDebugString);
+#endif
+        return result;
+    }
+};
 
 class PLATFORM_EXPORT DisplayItemList {
     WTF_MAKE_NONCOPYABLE(DisplayItemList);
@@ -141,8 +160,8 @@ public:
 
 protected:
     DisplayItemList()
-        : m_currentDisplayItems(kMaximumDisplayItemSize, 0)
-        , m_newDisplayItems(kMaximumDisplayItemSize, kInitialDisplayItemsCapacity * kMaximumDisplayItemSize)
+        : m_currentDisplayItems(0)
+        , m_newDisplayItems(kInitialDisplayItemsCapacity * kMaximumDisplayItemSize)
         , m_validlyCachedClientsDirty(false)
         , m_constructionDisabled(false)
         , m_skippingCacheCount(0)