Fix crash on incorrectly formatted MHTML documents

Source/core/loader/DocumentLoader.cpp

Index: Source/core/loader/DocumentLoader.cpp
diff --git a/Source/core/loader/DocumentLoader.cpp b/Source/core/loader/DocumentLoader.cpp
index 7feb915f6c3620b29fcc53db9137eea4292bbbe2..601b696340508e3c21916b2ccedb28788304b98f 100644
--- a/Source/core/loader/DocumentLoader.cpp
+++ b/Source/core/loader/DocumentLoader.cpp
@@ -286,9 +286,7 @@ void DocumentLoader::finishedLoading(double finishTime)
     if (!frameLoader())
         return;
 
-    if (isArchiveMIMEType(m_response.mimeType())) {
-        createArchive();
-    } else {
+    if (!isArchiveMIMEType(m_response.mimeType()) || !createArchive()) {

[Nate Chapin, 2014/01/06 23:04:11]

Should we consider changing this function's name back to maybeCreateArchive()
and move the isArchiveMIMEType() check into it?

That's how this code was a few months ago. I'm debating which one is more
readable.

[Inactive, 2014/01/07 00:38:17]

Done.

         // If this is an empty document, it will not have actually been created yet. Commit dummy data so that
         // DocumentWriter::begin() gets called and creates the Document.
         if (!m_writer)
@@ -645,11 +643,15 @@ bool DocumentLoader::isLoadingInAPISense() const
     return frameLoader()->subframeIsLoading();
 }
 
-void DocumentLoader::createArchive()
+bool DocumentLoader::createArchive()
 {
     ASSERT(m_mainResource);
     m_archive = MHTMLArchive::create(m_response.url(), m_mainResource->resourceBuffer());
-    RELEASE_ASSERT(m_archive);
+    // Invalid MHTML.
+    if (!m_archive || !m_archive->mainResource()) {
+        m_archive.clear();
+        return false;
+    }
 
     addAllArchiveResources(m_archive.get());
     ArchiveResource* mainResource = m_archive->mainResource();
@@ -659,6 +661,7 @@ void DocumentLoader::createArchive()
     ensureWriter(mainResource->mimeType(), m_archive->mainResource()->url());
 
     commitData(mainResource->data()->data(), mainResource->data()->size());
+    return true;
 }
 
 void DocumentLoader::addAllArchiveResources(MHTMLArchive* archive)