Disable subsequence caching when didLayoutWithPendingStylesheets is true.

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

Index: third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp b/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
index 0a6252bb97619ba13f0f2ee27db062730789b882..1adf2cf4b26de53dc455d7bb47cf4feeefa40dc0 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerPainter.cpp
+++ b/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().

[Xianzhu, 2016/03/23 03:44:56]

The comment above refer to methods that no longer exist. According to it, we
seem to do a full paint invalidation after the style sheets are loaded. I think
it's worth investigating which current methods the comments are supposed to
refer to and if the invalidation really happens and works and why if not. Could
you file a bug and add a TODO here?

[chrishtr, 2016/03/23 16:26:31]

Will send you a CL now to fix the comment.

-    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;
 }