net: Ignore the magic number sniffer if it determines an application/octet-st...

net/base/mime_sniffer.cc

Index: net/base/mime_sniffer.cc
===================================================================
--- net/base/mime_sniffer.cc	(revision 33698)
+++ net/base/mime_sniffer.cc	(working copy)
@@ -579,8 +579,14 @@
 
   // Now we look in our large table of magic numbers to see if we can find
   // anything that matches the content.
-  if (SniffForMagicNumbers(content, content_size, result))
+  if (SniffForMagicNumbers(content, content_size, result)) {
+    // We should never sniff an octet stream as plain text. There are Unix
+    // binaries with embedded shell scripts that get sniffed incorrectly,
+    // leading to spectacular failures like bug 29354.
+    if (type_hint == "application/octet-stream" && "text/plain" == *result)
+      result->assign("application/octet-stream");
     return true;  // We've matched a magic number.  No more content needed.
+  }
 
   // Having failed thus far, we're willing to override unknown mime types and
   // text/plain.