Add Uri.isScheme test function.

Add Uri.isScheme test function.

Allows checking the scheme of a URI against a known value.
Example: `uri.isScheme("http")`.
Has two advantages over `uri.scheme == "http"`:
* It's case insensitive, so you can do `uri.isScheme("HTTP")` as well, and
* for simple URIs, it doesn't need to allocate a new string.

R=floitsch@google.com

Committed: https://github.com/dart-lang/sdk/commit/dd561d513bcecb20e5995eccdd3843d529c0ec5b

[Lasse Reichstein Nielsen, 2017-01-27 09:48:29]

lrn@google.com changed reviewers:
+ floitsch@google.com

[Lasse Reichstein Nielsen, 2017-01-27 09:48:30]

lrn@google.com changed reviewers:
+ floitsch@google.com

[floitsch, 2017-01-30 11:17:44]

LGTM.

https://codereview.chromium.org/2664453003/diff/1/sdk/lib/core/uri.dart
File sdk/lib/core/uri.dart (right):

https://codereview.chromium.org/2664453003/diff/1/sdk/lib/core/uri.dart#newco...
sdk/lib/core/uri.dart:526: /// A `null` or empty [scheme] string will match if
the URI has no scheme
matches

[Lasse Reichstein Nielsen, 2017-01-30 12:26:43]

Description was changed from

==========
Add Uri.isScheme test function.

Allows checking the scheme of a URI against a known value.
Example: `uri.isScheme("http")`.
Has two advantages over `uri.scheme == "http"`:
* It's case insensitive, so you can do `uri.isScheme("HTTP")` as well, and
* for simple URIs, it doesn't need to allocate a new string.
==========

to

==========
Add Uri.isScheme test function.

Allows checking the scheme of a URI against a known value.
Example: `uri.isScheme("http")`.
Has two advantages over `uri.scheme == "http"`:
* It's case insensitive, so you can do `uri.isScheme("HTTP")` as well, and
* for simple URIs, it doesn't need to allocate a new string.

R=floitsch@google.com

Committed:
https://github.com/dart-lang/sdk/commit/dd561d513bcecb20e5995eccdd3843d529c0ec5b
==========

[Lasse Reichstein Nielsen, 2017-01-30 12:26:45]

Committed patchset #2 (id:20001) manually as
dd561d513bcecb20e5995eccdd3843d529c0ec5b (presubmit successful).