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

third_party/WebKit/Source/web/WebPageProblemDetector.h

+/*
+ * Copyright (C) 2017 Google Inc. All rights reserved.
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+ * modification, are permitted provided that the following conditions are
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+ * in the documentation and/or other materials provided with the
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+ *
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+ */
+
+#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_;
+};
+
+// A class which tries to gather information to determine if a page can be
+// treated as a blank page during page serialization as MHTML.
+class BlankPageDetector : public WebPageProblemDetector {
+  void VisitNode(const Node*) override;
+  void VisitingDone() override;
+};
+
+// A class which tries to gather information about number of missing images of a
+// page during page serialization as MHTML.
+class MissingImageDetector : public WebPageProblemDetector {

[Pete Williamson, 2017/05/17 00:31:48]

Let's move this and the CSS detector into their own header files (and remove the
blank page detector class).

[romax, 2017/05/17 22:28:19]

Done.

+ public:
+  void VisitNode(const Node*) override;
+  void VisitingDone() override;
+};
+
+// A class which tries to gather information about if the page is missing CSS
+// files during page serialization as MHTML.
+class MissingCSSDetector : public WebPageProblemDetector {
+ public:
+  void VisitNode(const Node*) override;
+  void VisitingDone() override;
+};
+
+}  // namespace blink
+#endif  // WebPageProblemDetector_h