Buffet: Implement fake HTTP transport to help write unit tests

Created fake Transport and Connection classes to help test
HTTP communications in Buffet. Now, when a fake transport
class is created a number of HTTP request handlers can be
registered, which will be called when a request to a web
server is made. These handlers can reply to the caller on
server's behalf and can provide response based on the
request data and parameters.

Removed 'static' from http::Request::range_value_omitted due
to a build break in debug (-O0) build. Static members should
be generally initialized in a .cc file, not header.

Fixed a bug in chromeos::url::GetQueryStringParameters() when
called on an empty string.

Finally, added 'bind_lamda.h' header file that adds the
ability to use lambdas in base::Bind() calls.

BUG=chromium:367377
TEST=Unit tests pass.

Change-Id: Ib4c070f676069f208b9df4da069ff3a29f8f656f
Reviewed-on: https://chromium-review.googlesource.com/197157
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/buffet/http_request.h b/buffet/http_request.h
index a93af94..62f4a01 100644
--- a/buffet/http_request.h
+++ b/buffet/http_request.h
@@ -305,7 +305,7 @@
   // range_value_omitted is used in |ranges_| list to indicate omitted value.
   // E.g. range (10,range_value_omitted) represents bytes from 10 to the end
   // of the data stream.
-  static const uint64_t range_value_omitted = (uint64_t)-1;
+  const uint64_t range_value_omitted = (uint64_t)-1;
 
   // Error message in case request fails completely.
   std::string error_;