Remove hidden elements from MHTML

third_party/WebKit/Source/web/WebFrameSerializer.cpp

Index: third_party/WebKit/Source/web/WebFrameSerializer.cpp
diff --git a/third_party/WebKit/Source/web/WebFrameSerializer.cpp b/third_party/WebKit/Source/web/WebFrameSerializer.cpp
index 08bb2044d4172f0023cc5bf3a4b64cc5ec7ed859..7b5b8b7b0964efb233eeb50d294f1f7704b4962e 100644
--- a/third_party/WebKit/Source/web/WebFrameSerializer.cpp
+++ b/third_party/WebKit/Source/web/WebFrameSerializer.cpp
@@ -81,6 +81,7 @@ class MHTMLFrameSerializerDelegate final : public FrameSerializer::Delegate {
  public:
   explicit MHTMLFrameSerializerDelegate(
       WebFrameSerializer::MHTMLPartsGenerationDelegate&);
+  bool shouldIgnoreElement(const Element&) override;
   bool shouldIgnoreAttribute(const Element&, const Attribute&) override;
   bool rewriteLink(const Element&, String& rewrittenLink) override;
   bool shouldSkipResourceWithURL(const KURL&) override;
@@ -96,6 +97,23 @@ MHTMLFrameSerializerDelegate::MHTMLFrameSerializerDelegate(
     WebFrameSerializer::MHTMLPartsGenerationDelegate& webDelegate)
     : m_webDelegate(webDelegate) {}
 
+bool MHTMLFrameSerializerDelegate::shouldIgnoreElement(const Element& element) {
+  // Do not include elements that are are set to hidden without affecting layout
+  // by the page. For those elements that are hidden by default, they will not
+  // be excluded:
+  // 1) All elements that are head or part of head, including head, meta, style,
+  //    link and etc.
+  // 2) Some specific elements in body: meta, datalist, option and etc.
+  if (element.layoutObject())
+    return false;
+  if (isHTMLHeadElement(element) || isHTMLMetaElement(element) ||
+      isHTMLDataListElement(element) || isHTMLOptionElement(element)) {
+    return false;
+  }
+  Element* parent = element.parentElement();
+  return parent && !isHTMLHeadElement(parent);
+}
+
 bool MHTMLFrameSerializerDelegate::shouldIgnoreAttribute(
     const Element& element,
     const Attribute& attribute) {