Add a will present block to the MDCSnackbarMessage class. This allows for clients who wish to customize their snackbar message view (MDCSnackbarMessageView) instance, but without exposing UI properties on the message objects. This also makes it easier for clients who have multiple files where they show the snackbar with only one Manager to not have issues with different classes stealing the MDCSnackbarDelegate in order to add customization to the snackbar view.

This new API when set to YES allows the Snackbar to be focused and stay on screen by issuing a UIAccessibilityLayoutChangedNotification on the snackbar message view.
When the Scheme is nil, the Snackbar gets weird colors and is presented wrong. Because Dragons doesn't receive a scheme, we need to explicitly create a scheme in each of the examples to fix the color for Snackbars.
Removes the need to copy-paste stanzas from other files anymore as we'll rely on #4478 to generate the correct stanza for us instead.
This was an automated change generated by running a find-and-replace regular expression:
```
/\*
Copyright ([0-9]+)-present the Material Components for iOS authors\. All Rights Reserved\.
Licensed under the Apache License, Version 2\.0 \(the "License"\);
you may not use this file except in compliance with the License\.
You may obtain a copy of the License at
http://www\.apache\.org/licenses/LICENSE-2\.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied\.
See the License for the specific language governing permissions and
limitations under the License\.
\*/
```
```
/\*
Copyright ([0-9]+)-present the Material Components for iOS authors\. All Rights Reserved\.
Licensed under the Apache License, Version 2\.0 \(the "License"\);
you may not use this file except in compliance with the License\.
You may obtain a copy of the License at
http://www\.apache\.org/licenses/LICENSE-2\.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied\.
See the License for the specific language governing permissions and
limitations under the License\.
\*/
```
```
/\*
Copyright ([0-9]+)-present the Material Components for iOS authors\. All Rights Reserved\.
Licensed under the Apache License, Version 2\.0 \(the "License"\);
you may not use this file except in compliance with the License\.
You may obtain a copy of the License at
http://www\.apache\.org/licenses/LICENSE-2\.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied\.
See the License for the specific language governing permissions and
limitations under the License\.
\*/
```
```
// Copyright $1-present the Material Components for iOS authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
```
* Replace MDC all icons
* Update border
* Replace MDCActionExtension icon with new logo
* Update all headers to be white on black
* Make Catalog greyscale to match Material’s style.
* Fix collection tile
* Update all headers to be white on black
* Make Catalog greyscale to match Material’s style.
* Fix collection tile
* WIP: Updating TabBar example to use black/green theme.
* WIP: Monochoroming all examples.
* Switch MDC Catalog to a black and white theme (#1355)
* Replace MDC all icons
* Update border
* Replace MDCActionExtension icon with new logo
* Update all headers to be white on black
* Make Catalog greyscale to match Material’s style.
* Fix collection tile
* Update all headers to be white on black
* Make Catalog greyscale to match Material’s style.
* Fix collection tile
* Fix floats
* Make Catalog greyscale to match Material’s style.
* More black and whiting
* WIP: Snackbar and global style
* Simplify snack bar examples.
* Page control
We can credit any contributor who would like to be credited this way, by adding them on request to the AUTHORS file. The copyright statement changes are required for this to work. Note that this has...
Summary:
We can credit any contributor who would like to be credited this way, by adding them on request to the AUTHORS file. The copyright statement changes are required for this to work. Note that this has no legal change, since the contributors always retained their copyright despite the copyright notice, but it's a nice acknowledgement.
Changed copyright statement to include non-Google authors.
Command run:
find * \( -name '*\.m' -or -name '*\.h' -or -name '*\.swift' \) -and -not \( -path 'scripts/external*' -name Pods \) -print0 | xargs -0 sed -i '' 's/Copyright \(.*\) Google Inc/Copyright \1 the Material Components for iOS authors/'
Added non-source files.
Command run:
grep -Rl 'Copyright .* Google Inc' * --exclude-dir scripts/external --null | xargs -0 sed -i '' 's/Copyright \(.*\) Google Inc/Copyright \1 the Material Components for iOS authors/'
Reviewers: featherless, O1 Material components iOS, randallli
Reviewed By: O1 Material components iOS, randallli
Tags: #material_components_ios
Differential Revision: http://codereview.cc/D1415
Summary:
Adds Snackbar and related Overlay Window component as well as demos for MDCCatalog. The Overlay component, of which Snackbar depends, is private for the time being.
- Removed dependencies on internal core.
- Removed i18n string translation, TODO added to replace.
- Removed RTL, waiting on https://github.com/google/material-components-ios/issues/579
- Animation curve constants moved inline.
- Fixed styling to be the material standard instead of configurable.
Reviewers: ajsecord, O1 Material components iOS
Reviewed By: ajsecord, O1 Material components iOS
Tags: #material_components_ios
Differential Revision: http://codereview.cc/D1036