Allow image documents in MHT if there is only one resource.

third_party/WebKit/Source/platform/mhtml/MHTMLArchive.cpp

 /*
  * Copyright (C) 2011 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
@@ skipping 60 matching lines @@
   // sandboxing enforcement on MHTML pages.
   if (!canLoadArchive(url))
     return nullptr;
 
   MHTMLParser parser(std::move(data));
   HeapVector<Member<ArchiveResource>> resources = parser.parseArchive();
   if (resources.isEmpty())
     return nullptr;  // Invalid MHTML file.
 
   MHTMLArchive* archive = new MHTMLArchive;
+
+  size_t resourcesCount = resources.size();
   // The first document suitable resource is the main resource of the top frame.
-  for (size_t i = 0; i < resources.size(); ++i) {
+  for (size_t i = 0; i < resourcesCount; ++i) {
+    if (archive->mainResource()) {
+      archive->addSubresource(resources[i].get());
+      continue;
+    }
+
     const AtomicString& mimeType = resources[i]->mimeType();
-    if (archive->mainResource() ||
-        !MIMETypeRegistry::isSupportedNonImageMIMEType(mimeType) ||
-        MIMETypeRegistry::isSupportedJavaScriptMIMEType(mimeType) ||
-        mimeType == "text/css")
+    bool isMimeTypeSuitableForMainResource =
+        MIMETypeRegistry::isSupportedNonImageMIMEType(mimeType);
+    // Want to allow image-only MHTML archives, but retain behavior for other
+    // documents that have already been created expecting the first HTML page to
+    // be considered the main resource.
+    if (resourcesCount == 1 &&
+        MIMETypeRegistry::isSupportedImageResourceMIMEType(mimeType)) {
+      isMimeTypeSuitableForMainResource = true;
+    }
+    // explicitly disallow JS and CSS as the main resource.
+    if (MIMETypeRegistry::isSupportedJavaScriptMIMEType(mimeType) ||
+        MIMETypeRegistry::isSupportedStyleSheetMIMEType(mimeType))
+      isMimeTypeSuitableForMainResource = false;
+
+    if (isMimeTypeSuitableForMainResource)
+      archive->setMainResource(resources[i].get());
+    else
       archive->addSubresource(resources[i].get());
-    else
-      archive->setMainResource(resources[i].get());
   }
   return archive;
 }
 
 bool MHTMLArchive::canLoadArchive(const KURL& url) {
   // MHTML pages can only be loaded from local URLs, http/https URLs, and
   // content URLs(Android specific).  The latter is now allowed due to full
   // sandboxing enforcement on MHTML pages.
   if (SchemeRegistry::shouldTreatURLSchemeAsLocal(url.protocol()))
     return true;
@@ skipping 149 matching lines @@
 ArchiveResource* MHTMLArchive::subresourceForURL(const KURL& url) const {
   return m_subresources.get(url.getString());
 }
 
 DEFINE_TRACE(MHTMLArchive) {
   visitor->trace(m_mainResource);
   visitor->trace(m_subresources);
 }
 
 }  // namespace blink