Add a URLRequest FTP fuzzer.

base/test/fuzzed_data_provider.h

Index: base/test/fuzzed_data_provider.h
diff --git a/base/test/fuzzed_data_provider.h b/base/test/fuzzed_data_provider.h
index 9f048f363e803dcadb12542fc1b5f61dbefe53c8..0750c36d30d3ca14d9364ebb5f02c0f28aec812e 100644
--- a/base/test/fuzzed_data_provider.h
+++ b/base/test/fuzzed_data_provider.h
@@ -33,6 +33,10 @@ class FuzzedDataProvider {
   // Returns a std::string containing all remaining bytes of the input data.
   std::string ConsumeRemainingBytes();
 
+  // Returns a std::string of length from 0 to |max_length|. When it runs out of
+  // input data, returns what remains of the input. Designed to be more stable with respect to inserting characters than picking a random length and then consuming that many bytes with ConsumeBytes().

[Charlie Harrison, 2016/11/01 19:02:05]

wrap to 80 cols.

[mmenke, 2016/11/01 19:14:29]

Done.  Oops.  Had to bypass the whine due to CR's in the corpus, which made me
miss the 80 col warning.

+  std::string ConsumeRandomLengthString(size_t max_length);

[Charlie Harrison, 2016/11/01 19:02:05]

Can you document that this looks for the magic string "\\"? Some consumers might
care about that. It would also be nice to explain why this is more stable, as it
isn't obvious (explanation can go in definition).

[mmenke, 2016/11/01 19:14:29]

I don't think it's useful to consumers unless we document all behavior here (The
ConsumeUint and friends pulling from the back of the input, for example).  Do we
want to do that?  I've added docs to the cc file, can move them, if we decide to
document all low level details in this file.

+
   // Returns a number in the range [min, max] by consuming bytes from the input
   // data. The value might not be uniformly distributed in the given range. If
   // there's no input data left, always returns |min|. |min| must be less than