[test] lazily parse css style rules

third_party/WebKit/Source/core/css/StyleSheetContents.h

Index: third_party/WebKit/Source/core/css/StyleSheetContents.h
diff --git a/third_party/WebKit/Source/core/css/StyleSheetContents.h b/third_party/WebKit/Source/core/css/StyleSheetContents.h
index ae3d78c6608c4ca89226a7272d245209d69698af..f1c1a227509f9986788313f8a2ee427148d5ba4c 100644
--- a/third_party/WebKit/Source/core/css/StyleSheetContents.h
+++ b/third_party/WebKit/Source/core/css/StyleSheetContents.h
@@ -159,6 +159,13 @@ public:
 
     String sourceMapURL() const { return m_sourceMapURL; }
 
+    void populateStringPool(const Vector<String> strings)
+    {
+        for (const auto& s : strings) {
+            m_stringPool.append(s);
+        }
+    }
+
     DECLARE_TRACE();
 
 private:
@@ -197,6 +204,7 @@ private:
 
     Member<RuleSet> m_ruleSet;
     String m_sourceMapURL;
+    Vector<String> m_stringPool;
 };
 
 } // namespace blink