add docs for datepicker keyboard

Author: tinayuangao

src/lib/datepicker/datepicker.md

@@ -229,5 +229,47 @@ application root module.
 export class MyApp {}
 ```
 ### Accessibility
-The input box for datepicker should have a placeholder or be given a meaningful label via
-`aria-label` or `aria-labelledby`.
+The `MdDatepickerInput` directive adds `aria-haspopup` attribute to the native input element, and it
+triggers a calendar dialog with `role="dialog"`.
+`MdDatepickerIntl` includes strings that are used for `aria-label`s. The datepicker input
+should have a placeholder or be given a meaningful label via `aria-label` or `aria-labelledby`.
+
+#### Keyboard shortcuts
+The keyboard shortcuts to handle datepicker are:
+`ALT` + `DOWN_ARROR`: trigger calendar dialog
+`ESCAPE`: close calendar dialog
+
+In month view:
+`LEFT_ARROW`, `RIGHT_ARROW`, `UP_ARROW`, `DOWN_ARROW`: navigate through days
+
+`HOME`: focus the first day of the month
+
+`END`: focus the last day of the month
+
+`PAGE_UP`: goes to previous month
+
+`ALT` + `PAGE_UP`: goes to previous year
+
+`PAGE_DOWN`: goes to next month
+
+`ALT` + `PAGE_DOWN`: goes to next year
+
+`ENTER`: select current focused date
+
+
+In year view:
+`LEFT_ARROW`, `RIGHT_ARROW`, `UP_ARROW`, `DOWN_ARROW`: navigate through months
+
+`HOME`: focus the first month of the year
+
+`END`: focus the last month of the year
+
+`PAGE_UP`: goes to previous year
+
+`ALT` + `PAGE_UP`: goes to previous 10 years
+
+`PAGE_DOWN`: goes to next year
+
+`ALT` + `PAGE_DOWN`: goes to next 10 years
+
+`ENTER`: select current focused month

src/lib/snack-bar/snack-bar.md

@@ -73,6 +73,7 @@ export class MessageArchivedComponent {
 }
 ```
 ### Accessibility
-A snack-bar automatically goes away after a short time, so you can't count on the user seeing the
-message or having a chance to press the button. For this reason, you should consider offering an
-alternate way to perform any snack-bar action.
+Snack-bar messages are announced via an `aria-live` region. Focus is not moved to
+the snack-bar element, as this would be disruptive to a user in the middle of a
+workflow. For any action offered in the snack-bar, the application should offer the
+user an alternative way to perform the action (typically via keyboard shortcut).

src/lib/toolbar/toolbar.md

@@ -51,5 +51,11 @@ use a neutral background color based on the current theme (light or dark). This
 `'primary'`, `'accent'`, or `'warn'`.  
 
 ### Accessibility
-Toolbar items without text or labels should be given a meaningful label via `aria-label` or
-`aria-labelledby`.
+By default, the toolbar assumes that it will be used in a purely decorative fashion and thus sets
+no roles, ARIA attributes, or keyboard shortcuts. This is equivalent to having a sequence of `<div>`
+elements on the page.
+
+Generally, the toolbar is used as a header where `role="header"` would be appropriate.
+
+Only if the use-case of the toolbar match that of role="toolbar", the user should add the role and
+an appropriate label via `aria-label` or `aria-labelledby`.