Disable subsequence caching when didLayoutWithPendingStylesheets is t…

…rue.

BUG=593758

Review URL: https://codereview.chromium.org/1823353003

Cr-Commit-Position: refs/heads/master@{#382791}

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

@@ -36,12 +36,12 @@
 
 namespace blink {
 
-static inline bool shouldSuppressPaintingLayer(PaintLayer* layer)
+static inline bool shouldSuppressPaintingLayer(const PaintLayer& layer)
 {
     // Avoid painting descendants of the root layer when stylesheets haven't loaded. This eliminates FOUC.
     // It's ok not to draw, because later on, when all the stylesheets do load, updateStyleSelector on the Document
     // will do a full paintInvalidationForWholeLayoutObject().
-    if (layer->layoutObject()->document().didLayoutWithPendingStylesheets() && !layer->isRootLayer() && !layer->layoutObject()->isDocumentElement())
+    if (layer.layoutObject()->document().didLayoutWithPendingStylesheets() && !layer.isRootLayer() && !layer.layoutObject()->isDocumentElement())
         return true;
 
     return false;
@@ -77,7 +77,7 @@ PaintLayerPainter::PaintResult PaintLayerPainter::paintLayer(GraphicsContext& co
     if (!m_paintLayer.isSelfPaintingLayer() && !m_paintLayer.hasSelfPaintingLayerDescendant())
         return FullyPainted;
 
-    if (shouldSuppressPaintingLayer(&m_paintLayer))
+    if (shouldSuppressPaintingLayer(m_paintLayer))
         return FullyPainted;
 
     if (m_paintLayer.layoutObject()->isLayoutView() && toLayoutView(m_paintLayer.layoutObject())->frameView()->shouldThrottleRendering())
@@ -209,6 +209,12 @@ static bool shouldCreateSubsequence(const PaintLayer& paintLayer, GraphicsContex
     if (!PaintLayerStackingNodeIterator(*paintLayer.stackingNode(), AllChildren).next())
         return false;
 
+    // When in FOUC-avoidance mode, don't cache any subsequences, to avoid having
+    // to invalidate all of them when leaving this mode. There is an early-out in BlockPainter::paintContents that may result
+    // in nothing getting painted in thos mode, in addition to early-out logic in PaintLayerPainter.
+    if (paintLayer.layoutObject()->document().didLayoutWithPendingStylesheets())
+        return false;
+
     return true;
 }
 

third_party/WebKit/Source/web/tests/DocumentLoadingRenderingTest.cpp

@@ -4,6 +4,8 @@
 
 #include "core/dom/Document.h"
 #include "core/html/HTMLIFrameElement.h"
+#include "core/layout/LayoutView.h"
+#include "core/paint/PaintLayer.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "web/tests/sim/SimCompositor.h"
 #include "web/tests/sim/SimDisplayItemList.h"
@@ -270,6 +272,14 @@ TEST_F(DocumentLoadingRenderingTest, ShouldNotPaintIframeContentWithPendingSheet
     // invalid paint so we shouldn't draw any text.
     EXPECT_FALSE(frame2.containsText());
 
+    LayoutView* iframeLayoutView = childFrame->contentDocument()->layoutView();
+    const DisplayItemList& displayItemList = iframeLayoutView->layer()->graphicsLayerBacking()->getPaintController().getDisplayItemList();
+    // Check that the DisplayItemList has no subsequene caching markers. These are not allowed in pending-style-sheets mode
+    // since otherwise caching would be incorrect.
+    ASSERT_EQ(2u, displayItemList.size());
+    EXPECT_EQ(DisplayItem::DocumentBackground, displayItemList[0].getType());
+    EXPECT_EQ(DisplayItem::BoxDecorationBackground, displayItemList[1].getType());
+
     // 1 for the main frame background (white),
     // 1 for the iframe background (pink)
     // 1 for the composited transform layer in the iframe (green).