Avoid synchronous stylesheet update on html import loaded.

third_party/WebKit/Source/core/dom/TreeScopeStyleSheetCollection.cpp

Index: third_party/WebKit/Source/core/dom/TreeScopeStyleSheetCollection.cpp
diff --git a/third_party/WebKit/Source/core/dom/TreeScopeStyleSheetCollection.cpp b/third_party/WebKit/Source/core/dom/TreeScopeStyleSheetCollection.cpp
index 5380b66c510d8a021290426381865f7826458fc9..cfff0c100a87c1ba436ba985e4855b3e9541c43f 100644
--- a/third_party/WebKit/Source/core/dom/TreeScopeStyleSheetCollection.cpp
+++ b/third_party/WebKit/Source/core/dom/TreeScopeStyleSheetCollection.cpp
@@ -35,6 +35,7 @@
 #include "core/css/resolver/StyleResolver.h"
 #include "core/dom/Element.h"
 #include "core/dom/StyleEngine.h"
+#include "core/dom/StyleSheetCandidate.h"
 #include "core/html/HTMLLinkElement.h"
 #include "core/html/HTMLStyleElement.h"
 
@@ -69,6 +70,15 @@ void TreeScopeStyleSheetCollection::ApplyActiveStyleSheetChanges(
   new_collection.Swap(*this);
 }
 
+bool TreeScopeStyleSheetCollection::HasStyleSheets() const {
+  for (Node* node : style_sheet_candidate_nodes_) {
+    StyleSheetCandidate candidate(*node);
+    if (candidate.Sheet() || candidate.IsEnabledAndLoading())
+      return true;
+  }
+  return false;
+}
+
 DEFINE_TRACE(TreeScopeStyleSheetCollection) {
   visitor->Trace(tree_scope_);
   visitor->Trace(style_sheet_candidate_nodes_);