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..0c1b9ee52daaca047cfa2880d8698c844b8eb60b 100644
--- a/net/base/mime_sniffer.h
+++ b/net/base/mime_sniffer.h
@@ -41,6 +41,19 @@ NET_EXPORT bool SniffMimeType(const char* content, size_t content_size,
                               const GURL& url, const std::string& type_hint,
                               std::string* result);
 
+// Guess 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.

[Ryan Sleevi, 2013/05/03 19:03:24]

So I realize that you plan to work with Adam to address (further) feedback on
this Monday, but it would be good to add a comment indicating the
appropriateness - or inappropriateness - of calling this function.

eg:
"Note: This should not be used when handling data that comes from untrusted
sources - eg: a network or filesystem. For such cases, use SniffMimeType, which
is meant to strictly adhere to http://mimesniff.spec.whatwg.org/ and be
compatible/inter-operable with other implementations.

IdentifyExtraMimeType may be used to [...]"

Or just *SOMETHING* to indicate that this is not a blank cheque to go calling
this function willy nilly. I'm sure Adam will have a much better comment
suggestion on his return.

[abarth-chromium, 2013/05/06 17:54:11]

Yeah, I think it's important to pick a name for this function and to add a
comment explaining when it's appropriate to call each function.

Generally speaking, SniffMimeType should be called for untrusted data and for
network traffic.  The new function should can be called only for trusted, local
data.

+//
+// @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 IdentifyExtraMimeType(const char* content,

[abarth-chromium, 2013/05/06 17:54:59]

Maybe "SniffMimeTypeFromTrustedLocalData" would be a better name?

+                                      size_t content_size,
+                                      std::string* result);
+
 }  // namespace net
 
 #endif  // NET_BASE_MIME_SNIFFER_H__