docs: studio support library revisions update

<p>This section provides details about the Support Library package releases.</p>

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  <p id="rev21"><a href="#" onclick="return toggleContent(this)">

    <img src="{@docRoot}assets/images/triangle-opened.png" class="toggle-content-img" alt=""

/>Android Support Library, revision 21.0.3</a> <em>(December 2014)</em>

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    <dl>

      <dt>Changes for <a href="features.html#v4">v4 support library:</a></dt>

      <dd>

        <ul>

          <li>Added several {@link android.support.v4.app.NotificationCompat.WearableExtender}

          methods to improve the display of barcodes in notifications on wearable devices.

             <ul>

             <li>{@link android.support.v4.app.NotificationCompat.WearableExtender#getHintScreenTimeout getHintScreenTimeout()}</li>

             <li>{@link android.support.v4.app.NotificationCompat.WearableExtender#setHintScreenTimeout setHintScreenTimeout()}</li>

             <li>{@link android.support.v4.app.NotificationCompat.WearableExtender#getHintAvoidBackgroundClipping getHintAvoidBackgroundClipping()}</li>

             <li>{@link android.support.v4.app.NotificationCompat.WearableExtender#setHintAvoidBackgroundClipping setHintAvoidBackgroundClipping()}</li>

             </ul>

          </li>

        </ul>

      </dd>

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  <p id="rev21"><a href="#" onclick="return toggleContent(this)">

    <img src="{@docRoot}assets/images/triangle-closed.png" class="toggle-content-img" alt=""

/>Android Support Library, revision 21.0.2</a> <em>(November 2014)</em>

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    <dl>

      <dt>Changes for <a href="features.html#v4">v4 support library:</a></dt>

      <dd>

        <ul>

          <li>Added {@link android.support.v4.app.NotificationCompat.CarExtender}

          class to support Android Auto extensions to notifications.</li>

        </ul>

      </dd>

      <dt>Changes for <a href="features.html#v7-appcompat">v7 appcompat library</a>:</dt>

      <dd>

        <ul>

          <li>Added the {@link android.support.v7.widget.PopupMenu} constructor to support new popup

          menus.</li>

          <li>Added support for a Collapse icon description in the {@link android.support.v7.widget.Toolbar}

          class.</li>

          <li>Updated the {@link android.support.v7.widget.SearchView} widget to support displaying

          the {@link android.support.v7.mediarouter.R.attr#commitIcon}. </li>

          <li>Removed the <code>buttonGravity</code> attribute from the

          {@link android.support.v7.widget.Toolbar} class. </li>

        </ul>

      </dd>

      <dt>Changes for <a href="features.html#v7-cardview">v7 cardview library</a>:</dt>

      <dd>

        <ul>

          <li>Added {@link android.support.v7.widget.CardView#setCardBackgroundColor} API to

          support changing the background color of the {@link android.support.v7.widget.CardView}.</li>

          <li>Changed the {@link android.support.v7.widget.CardView} to more accurately report its

          opacity value as {@link android.graphics.PixelFormat#TRANSLUCENT}.</li>

        </ul>

      </dd>

      <dt>Changes for <a href="features.html#v7-recyclerview">v7 recyclerview

        library</a>:</dt>

      <dd>

        <ul>

          <li>Added {@link android.support.v7.widget.RecyclerView#TOUCH_SLOP_DEFAULT} and

          {@link android.support.v7.widget.RecyclerView#TOUCH_SLOP_PAGING} constants

          to the {@link android.support.v7.widget.RecyclerView} class

          to support touch slop configurations for paging.</li>

        </ul>

      </dd>

      <dt>Changes for <a href="features.html#v17-leanback">v17 leanback library</a>:</dt>

      <dd>

        <ul>

          <li>Added support to generate v4 code fragments. </li>

          <li>Changed the secondary text color on {@link android.support.v7.widget.CardView}. </li>

        </ul>

      </dd>

    </dl>

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  <p id="rev21"><a href="#" onclick="return toggleContent(this)">

    <img src="{@docRoot}assets/images/triangle-closed.png" class="toggle-content-img" alt=""

/>Android Support Library, revision 21.0.1</a> <em>(November 2014)</em>

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    <dl>

      <dt>Added <a href="{@docRoot}tools/support-library/features.html#multidex">

      multidex support library</a> to support multiple

      <a href="https://source.android.com/devices/tech/dalvik/">Dalvik</a> Executable (DEX) files

      for multi-dex file support prior to Android 5.0. </li>

      </dt>

    </dl>

  </div>

</div>

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  <p id="rev21"><a href="#" onclick="return toggleContent(this)">

    <img src="{@docRoot}assets/images/triangle-closed.png" class="toggle-content-img" alt=""

/>Android Support Library, revision 21</a> <em>(October 2014)</em>

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