[Offline Pages] Adding missing image/CSS detection in FrameSerializer.

third_party/WebKit/Source/core/frame/FrameSerializer.h

Index: third_party/WebKit/Source/core/frame/FrameSerializer.h
diff --git a/third_party/WebKit/Source/core/frame/FrameSerializer.h b/third_party/WebKit/Source/core/frame/FrameSerializer.h
index b53d02d984a0f7defee3763e8f5217ef5ff9e5fd..cc88445d7f758bb831841f7a1a607065f2bdd9a1 100644
--- a/third_party/WebKit/Source/core/frame/FrameSerializer.h
+++ b/third_party/WebKit/Source/core/frame/FrameSerializer.h
@@ -107,6 +107,8 @@ class CORE_EXPORT FrameSerializer final {
     virtual Vector<Attribute> GetCustomAttributes(const Element&) {
       return Vector<Attribute>();
     }
+
+    virtual bool ShouldCollectProblemMetric() { return false; }
   };
 
   // Constructs a serializer that will write output to the given deque of
@@ -151,6 +153,13 @@ class CORE_EXPORT FrameSerializer final {
   bool is_serializing_css_;
 
   Delegate& delegate_;
+
+  // Variables for problem detection during serialization.
+  int total_image_count_;
+  int loaded_image_count_;
+  int total_css_count_;
+  int loaded_css_count_;
+  bool should_collect_problem_metric_;
 };
 
 }  // namespace blink