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

third_party/WebKit/Source/web/WebPageProblemDetector.h

Index: third_party/WebKit/Source/web/WebPageProblemDetector.h
diff --git a/third_party/WebKit/Source/web/WebPageProblemDetector.h b/third_party/WebKit/Source/web/WebPageProblemDetector.h
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+/*
+ * Copyright (C) 2017 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef WebPageProblemDetector_h
+#define WebPageProblemDetector_h
+
+#include <memory>
+#include <vector>
+
+namespace blink {
+
+class Node;
+
+// Interface for individual web page problem detector, which will be called
+// through MHTMLFrameSerializerDelegate on each of the node during DOM walking
+// when serializing a page as MHTML.
+class WebPageProblemDetector {
+ public:
+  // Visits a node in the DOM tree.
+  virtual void VisitNode(const Node*) = 0;
+  // Called when the visiting finishes.
+  virtual void VisitingDone() = 0;
+};
+
+// Holds all problem detectors so we can visit all of them.
+class WebPageProblemDetectorCollection : public WebPageProblemDetector {
+ public:
+  // Used to register a problem detector.
+  void AddDetector(std::unique_ptr<WebPageProblemDetector>);
+
+  // When we are visiting a node, call all registered problem observers and give
+  // them an opportunity to examine the node.
+  void VisitNode(const Node*) override;
+
+  // When the DOM walk is over, give each detector a chance to compute and
+  // report results.
+  void VisitingDone() override;
+
+ private:
+  std::vector<std::unique_ptr<WebPageProblemDetector>> detectors_;
+};
+
+}  // namespace blink
+#endif  // WebPageProblemDetector_h