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..e19adfdd0383471053601b798bd1c092cea06843 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositingRequirementsUpdater.cpp
@@ -539,6 +539,24 @@ void CompositingRequirementsUpdater::updateRecursive(
         anyDescendantHas3DTransform || layer->has3DTransform();
   }
 
+  // Promote skewed elements within a promoted skewed element to improve
+  // output quality.
+  if (canBeComposited && ancestorLayer &&
+      ancestorLayer->getCompositingReasons()) {

[flackr, 2017/02/25 15:16:19]

Only if the ancestor was also skewed. If the ancestor layer was not skewed then
we don't need to promote skewed descendants. We might need to make this part of
CompositingRequirementsUpdater::RecursionData so that we don't have to search up
the tree every time.

[yigu, 2017/02/27 22:03:41]

Done.

+    if (layer->layoutObject().styleRef().hasTransform()) {
+      for (const auto& operation :
+           layer->layoutObject().styleRef().transform().operations()) {

[flackr, 2017/02/25 15:16:19]

Move this to TransformOperations::hasSkew.

[yigu, 2017/02/27 22:03:42]

Done.

+        TransformOperation::OperationType type = operation->type();
+        if (type == TransformOperation::Skew ||
+            type == TransformOperation::SkewX ||
+            type == TransformOperation::SkewY) {
+          reasonsToComposite |=
+              CompositingReasonLayerForTextWithinSkewedPromotedElement;
+        }
+      }
+    }
+  }
+
   // At this point we have finished collecting all reasons to composite this
   // layer.
   layer->setCompositingReasons(reasonsToComposite);