Fix unexpected blurry text caused by combination of skew and promotion

third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp
index aca28342b55b0d8d63095c2406bf06611a14e85a..79f55aebac9e705df76d850fb57b51ec7cc877a8 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp
@@ -154,6 +154,12 @@ class CompositingRequirementsUpdater::RecursionData {
   bool m_hasUnisolatedCompositedBlendingDescendant;
   bool m_testingOverlap;
   bool m_hasCompositedScrollingAncestor;
+  Vector<PaintLayer*>& layersNeedingPostProcessing() {
+    return m_layersNeedingPostProcessing;
+  }
+
+ private:
+  Vector<PaintLayer*> m_layersNeedingPostProcessing;
 };
 
 static bool requiresCompositingOrSquashing(CompositingReasons reasons) {
@@ -517,6 +523,35 @@ void CompositingRequirementsUpdater::updateRecursive(
     if (willBeCompositedOrSquashed)
       currentRecursionData.m_subtreeIsCompositing = true;
 
+    // Track non-composited skewed elements
+    if (!willBeCompositedOrSquashed && canBeComposited &&
+        layer->layoutObject().styleRef().hasTransform() &&
+        layer->layoutObject().styleRef().transform().hasSkew()) {
+      currentRecursionData.layersNeedingPostProcessing().push_back(layer);
+    }
+
+    // Promote skewed elements within a promoted skewed element to improve
+    // output quality.
+    if (willBeCompositedOrSquashed &&
+        !childRecursionData.layersNeedingPostProcessing().isEmpty()) {
+      // If an skewed element is composited due to its descendants, we have to
+      // update the uncomposited skewed descendants to composite them.
+      if (layer->layoutObject().styleRef().hasTransform() &&
+          layer->layoutObject().styleRef().transform().hasSkew()) {
+        for (auto& childLayer :
+             childRecursionData.layersNeedingPostProcessing()) {
+          childLayer->setCompositingReasons(
+              CompositingReasonSkewWithCompositedSkewedAncestor);
+        }
+      }
+      childRecursionData.layersNeedingPostProcessing().clear();
+    }
+
+    // Current non-leaf layer and it descendants have been updated.
+    if (layer->firstChild()) {
+      currentRecursionData.layersNeedingPostProcessing().clear();
+    }
+
     // Turn overlap testing off for later layers if it's already off, or if we
     // have an animating transform.  Note that if the layer clips its
     // descendants, there's no reason to propagate the child animation to the