Have media gallery (through native media file util) use MIME sniffer

net/base/mime_sniffer.h

Index: net/base/mime_sniffer.h
diff --git a/net/base/mime_sniffer.h b/net/base/mime_sniffer.h
index 9cdb2d709c76f185c1a096d3f3e4ddeccd96f44a..77f3833fe85e799bd5ec90cf2463d99da3bb6edd 100644
--- a/net/base/mime_sniffer.h
+++ b/net/base/mime_sniffer.h
@@ -41,6 +41,22 @@ NET_EXPORT bool SniffMimeType(const char* content, size_t content_size,
                               const GURL& url, const std::string& type_hint,
                               std::string* result);
 
+// Attempt to identify a MIME type from the first few bytes of content only.
+// Uses a bigger set of media file searches than |SniffMimeType()|.
+// If finds a match, fills in |result| and returns true,
+// otherwise returns false.
+//
+// The caller should understand the security ramifications of trusting
+// uncontrolled data before accepting the results of this function.
+//
+// @param content A buffer containing the bytes to sniff.
+// @param content_size The number of bytes in the |content| buffer.
+// @param result Address at which to place the sniffed mime type.
+// @return Returns true if a MIME type match was found.
+NET_EXPORT bool SniffMimeTypeFromLocalData(const char* content,
+                                           size_t content_size,
+                                           std::string* result);
+
 }  // namespace net
 
 #endif  // NET_BASE_MIME_SNIFFER_H__