docs: Removed obsolete links to Android N Preview Reference.

        <li><a href="#vr">VR Support</a></li>

        <li><a href="#print_svc">Print Service Enhancements</a></li>

        <li><a href="#virtual_files">Virtual Files</a></li>

        <li><a href="#framemetrics_api">FrameMetricsListener API</a></li>

        <li><a href="#framemetrics_api">Frame Metrics API</a></li>

      </ol>

</div>

</div>

</p>

<p>

  For information about creating an app tile, see the documentation for

  <code>android.service.quicksettings.Tile</code> in the downloadable <a href=

  "{@docRoot}preview/setup-sdk.html#docs-dl">API Reference</a>.

  For information about creating an app tile, see the reference documentation

  for {@link android.service.quicksettings.Tile Tile}.

</p>

through any medium, such as a VOIP endpoint or forwarding phones.</p>

<p>

  For more information, see <code>android.provider.BlockedNumberContract</code>

  in the downloadable <a href="{@docRoot}preview/setup-sdk.html#docs-dl">API

  Reference</a>.

  For more information, see the reference documentation for

  {@link android.provider.BlockedNumberContract BlockedNumberContract}.

</p>

<h2 id="call_screening">Call Screening</h2>

</ul>

<p>

  For more information, see <code>android.telecom.CallScreeningService</code>

  in the downloadable <a href="{@docRoot}preview/setup-sdk.html#docs-dl">API

  Reference</a>.

  For more information, see the reference documentation for

  {@link android.telecom.CallScreeningService CallScreeningService}.

</p>

features such as face-tracking, eye-tracking, point scanning, and so on, to

meet the needs of those users.</p>

<p>For more information, see <code>android.accessibilityservice.GestureDescription</code>

  in the downloadable <a href="{@docRoot}preview/setup-sdk.html#docs-dl">API Reference</a>.</p>

<p>For more information, see the reference documentation for

{@link android.accessibilityservice.GestureDescription GestureDescription}.

</p>

<h2 id="direct_boot">Direct Boot</h2>

  from the system and from the app in focus. The system retrieves these

  shortcuts automatically from the app’s menu if the shortcuts exist. You can

  also provide your own fine-tuned shortcuts lists for the screen. You can do

  this by overriding the new <code>Activity.onProvideKeyboardShortcuts()</code>

  method, described in the downloadable <a href=

  "{@docRoot}preview/setup-sdk.html#docs-dl">API Reference</a>.

  this by overriding the {@link android.view.Window.Callback#onProvideKeyboardShortcuts

  onProvideKeyboardShortcuts()} method.

</p>

<p class="note">

<p>

  To trigger Keyboard Shortcuts Helper from anywhere in your app, call

  {@code Activity.requestKeyboardShortcutsHelper()} for the relevant activity.

  {@link android.app.Activity#requestShowKeyboardShortcuts requestShowKeyboardShortcuts()}

  from the relevant activity.

</p>

<h2 id="custom_pointer_api">

<ul>

  <li>You can set an icon from a resource ID by calling

  <code>PrinterInfo.Builder.setResourceIconId()</code>

  {@link android.print.PrinterInfo.Builder#setIconResourceId setIconResourceId()}.

  </li>

  <li>You can show an icon from the network by calling

  <code>PrinterInfo.Builder.setHasCustomPrinterIcon()</code>, and setting a

  callback for when the icon is requested using

  <code>android.printservice.PrinterDiscoverySession.onRequestCustomPrinterIcon()</code>

  {@link android.print.PrinterInfo.Builder#setHasCustomPrinterIcon setHasCustomPrinterIcon()},

  and setting a callback for when the icon is requested using

  {@link android.printservice.PrinterDiscoverySession#onRequestCustomPrinterIcon onRequestCustomPrinterIcon()}.

  </li>

</ul>

<p>

  In addition, you can provide a per-printer activity to display additional

  information by calling <code>PrinterInfo.Builder.setInfoIntent()</code>.

  information by calling {@link android.print.PrinterInfo.Builder#setInfoIntent setInfoIntent()}.

</p>

<p>

  You can indicate the progress and status of print jobs in the print job

  notification by calling

  <code>android.printservice.PrintJob.setProgress()</code> and

  <code>android.printservice.PrintJob.setStatus()</code>, respectively.

</p>

<p>

  For more information about these methods, see the downloadable <a href=

  "{@docRoot}preview/setup-sdk.html#docs-dl">API Reference</a>.

  {@link android.printservice.PrintJob#setProgress setProgress()} and

  {@link android.printservice.PrintJob#setStatus setStatus()}, respectively.

</p>

<h2 id="framemetrics_api">FrameMetricsListener API</h2>

<h2 id="framemetrics_api">Frame Metrics API</h2>

<p>

The FrameMetricsListener API allows an app to monitor its UI rendering

The Frame Metrics API allows an app to monitor its UI rendering

performance. The API provides this capability by exposing a streaming Pub/Sub API to transfer frame

timing info for the app's current window. The data returned is

equivalent to that which <code><a href="{@docRoot}tools/help/shell.html#shellcommands">adb shell</a>

</p>

<p>

You can use FrameMetricsListener to measure interaction-level UI

You can use the Frame Metrics API to measure interaction-level UI

performance in production, without a USB connection. This API

allows collection of data at a much higher granularity than does

{@code adb shell dumpsys gfxinfo}. This higher granularity is possible because

</p>

<p>

To monitor a window, implement the <code>FrameMetricsListener.onMetricsAvailable()</code>

callback method and register it on that window. For more information, refer to

the {@code FrameMetricsListener} class documentation in

the downloadable <a href="{@docRoot}preview/setup-sdk.html#docs-dl">API Reference</a>.

To monitor a window, implement the

{@link android.view.Window.OnFrameMetricsAvailableListener#onFrameMetricsAvailable OnFrameMetricsAvailableListener.onFrameMetricsAvailable()}

callback method and register it on that window.

</p>

<p>

The API provides a {@code FrameMetrics} object, which contains timing data that

the rendering subsystem reports for various milestones in a frame lifecycle.

The supported metrics are: {@code UNKNOWN_DELAY_DURATION},

The API provides a {@link android.view.FrameMetrics FrameMetrics} object, which

contains timing data that the rendering subsystem reports for various milestones

in a frame lifecycle. The supported metrics are: {@code UNKNOWN_DELAY_DURATION},

{@code INPUT_HANDLING_DURATION}, {@code ANIMATION_DURATION},

{@code LAYOUT_MEASURE_DURATION}, {@code DRAW_DURATION}, {@code SYNC_DURATION},

{@code COMMAND_ISSUE_DURATION}, {@code SWAP_BUFFERS_DURATION},