3 files changed, 17 insertions, 1 deletions
diff --git a/chrome/browser/resource_dispatcher_host.cc b/chrome/browser/resource_dispatcher_host.cc
index 597abba..85a0fb8 100644
--- a/chrome/browser/resource_dispatcher_host.cc
+++ b/chrome/browser/resource_dispatcher_host.cc
@@ -1179,6 +1179,7 @@ bool ResourceDispatcherHost::BufferedEventHandler::KeepBuffering(
       // SniffMimeType() returns false if there is not enough data to determine
       // the mime type. However, even if it returns false, it returns a new type
       // that is probably better than the current one.
+      DCHECK(bytes_read_ < 512 /*kMaxBytesToSniff*/);
       if (!finished_) {
         buffering_ = true;
         return true;
diff --git a/net/base/mime_sniffer.cc b/net/base/mime_sniffer.cc
index 53e765e..da117e2 100644
--- a/net/base/mime_sniffer.cc
+++ b/net/base/mime_sniffer.cc
@@ -529,7 +529,9 @@ bool SniffMimeType(const char* content, size_t content_size,
     // We're not interested in sniffing these types for images and the like.
     // Instead, we're looking explicitly for a feed.  If we don't find one we're
     // done and return early.
-    return SniffXML(content, content_size, result);
+    if (SniffXML(content, content_size, result))
+      return true;
+    return content_size >= kMaxBytesToSniff;
   }
 
   // Now we look in our large table of magic numbers to see if we can find
diff --git a/net/base/mime_sniffer_unittest.cc b/net/base/mime_sniffer_unittest.cc
index 0ed87e8..caf258b 100644
--- a/net/base/mime_sniffer_unittest.cc
+++ b/net/base/mime_sniffer_unittest.cc
@@ -295,3 +295,16 @@ TEST(MimeSnifferTest, XMLTest) {
 
 }
 
+// Test content which is >= 512 bytes, and includes no open angle bracket.
+// http://code.google.com/p/chromium/issues/detail?id=3521
+TEST(MimeSnifferTest, XMLTestLargeNoAngledBracket) {
+  // Make a large input, with 600 bytes of "x". 
+  std::string content;
+  content.resize(600);
+  std::fill(content.begin(), content.end(), 'x');
+
+  // content.size() >= kMaxBytesToSniff (512) so the sniff is unambiguous.
+  std::string mime_type;
+  EXPECT_TRUE(net::SniffMimeType(content.data(), content.size(), GURL(),
+                                 "text/xml", &mime_type));
+}