Oilpan: promptly dispose style resolvers upon clearing.

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

Index: third_party/WebKit/Source/core/dom/TreeScope.cpp
diff --git a/third_party/WebKit/Source/core/dom/TreeScope.cpp b/third_party/WebKit/Source/core/dom/TreeScope.cpp
index 4873cbde4de5fc9115650dcbeb553b49af68fb0f..1edd0226d4705e182ece56901cd13152d6c3eda0 100644
--- a/third_party/WebKit/Source/core/dom/TreeScope.cpp
+++ b/third_party/WebKit/Source/core/dom/TreeScope.cpp
@@ -156,6 +156,13 @@ ScopedStyleResolver& TreeScope::ensureScopedStyleResolver()
 
 void TreeScope::clearScopedStyleResolver()
 {
+#if ENABLE(OILPAN)
+    if (m_scopedStyleResolver) {
+        // See StyleEngine::clearResolver() for the motivation for
+        // this explicit disposal step. Same applies for ScopedStyleResolvers.
+        m_scopedStyleResolver->dispose();
+    }
+#endif
     m_scopedStyleResolver.clear();
 }