Paint collapsed borders of a table as one display item

third_party/WebKit/Source/core/paint/TablePainter.cpp

Index: third_party/WebKit/Source/core/paint/TablePainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/TablePainter.cpp b/third_party/WebKit/Source/core/paint/TablePainter.cpp
index 16f910484ae6263f1cb44bbaf6332af82bd83f8f..cfa0975c799fd5595bf15b6117913e09e7cd3ccb 100644
--- a/third_party/WebKit/Source/core/paint/TablePainter.cpp
+++ b/third_party/WebKit/Source/core/paint/TablePainter.cpp
@@ -44,31 +44,54 @@ void TablePainter::paintObject(const PaintInfo& paintInfo,
       }
     }
 
-    if (m_layoutTable.collapseBorders() &&
-        shouldPaintDescendantBlockBackgrounds(paintPhase) &&
-        m_layoutTable.style()->visibility() == EVisibility::Visible) {
-      // Using our cached sorted styles, we then do individual passes,
-      // painting each style of border from lowest precedence to highest
-      // precedence.
-      LayoutTable::CollapsedBorderValues collapsedBorders =
-          m_layoutTable.collapsedBorders();
-      size_t count = collapsedBorders.size();
-      for (size_t i = 0; i < count; ++i) {
-        for (LayoutTableSection* section = m_layoutTable.bottomSection();
-             section; section = m_layoutTable.sectionAbove(section)) {
-          LayoutPoint childPoint =
-              m_layoutTable.flipForWritingModeForChild(section, paintOffset);
-          TableSectionPainter(*section).paintCollapsedBorders(
-              paintInfoForDescendants, childPoint, collapsedBorders[i]);
-        }
-      }
-    }
+    if (shouldPaintDescendantBlockBackgrounds(paintPhase))
+      paintCollapsedBorders(paintInfoForDescendants, paintOffset);
   }
 
   if (shouldPaintSelfOutline(paintPhase))
     ObjectPainter(m_layoutTable).paintOutline(paintInfo, paintOffset);
 }
 
+void TablePainter::paintCollapsedBorders(const PaintInfo& paintInfo,
+                                         const LayoutPoint& paintOffset) {
+  if (!m_layoutTable.hasCollapsedBorders() ||
+      m_layoutTable.style()->visibility() != EVisibility::Visible)
+    return;
+
+  LayoutTable::CollapsedBordersInfo& collapsedBorders =
+      m_layoutTable.getCollapsedBordersInfo();
+  if (paintInfo.context.getPaintController().clientCacheIsValid(

[wkorman, 2016/11/03 05:26:13]

This looks like the first call of clientCacheIsValid() outside of
PaintController itself, may be worth a comment noting that this is unusual since
painting collapsed borders is itself unusual and so we manage its cache
invalidation specially. Or maybe we expect there may be more calls to
clientCacheIsValid() for similar cases later. Figured worth mentioning since it
caught my eye.

[Xianzhu, 2016/11/03 16:06:13]

Done.

+          m_layoutTable) &&
+      collapsedBorders.lastPaintResult != FullyPainted &&
+      collapsedBorders.lastPaintRect != paintInfo.cullRect())
+    m_layoutTable.setDisplayItemsUncached();
+
+  if (!DrawingRecorder::useCachedDrawingIfPossible(
+          paintInfo.context, m_layoutTable,
+          DisplayItem::kTableCollapsedBorders)) {
+    DrawingRecorder recorder(
+        paintInfo.context, m_layoutTable, DisplayItem::kTableCollapsedBorders,
+        FloatRect(LayoutRect(paintOffset, m_layoutTable.size())));
+
+    // Using our cached sorted styles, we then do individual passes, painting
+    // each style of border from lowest precedence to highest precedence.
+    PaintResult paintResult = FullyPainted;
+    for (const auto& borderValue : collapsedBorders.values) {
+      for (LayoutTableSection* section = m_layoutTable.bottomSection(); section;
+           section = m_layoutTable.sectionAbove(section)) {
+        LayoutPoint childPoint =
+            m_layoutTable.flipForWritingModeForChild(section, paintOffset);
+        if (TableSectionPainter(*section).paintCollapsedBorders(
+                paintInfo, childPoint, borderValue) ==
+            MayBeClippedByPaintDirtyRect)
+          paintResult = MayBeClippedByPaintDirtyRect;
+      }
+    }
+    collapsedBorders.lastPaintResult = paintResult;
+    collapsedBorders.lastPaintRect = paintInfo.cullRect();
+  }
+}
+
 void TablePainter::paintBoxDecorationBackground(
     const PaintInfo& paintInfo,
     const LayoutPoint& paintOffset) {