title: Material design - left margins for action bar title and content don't match
body: <p>I'm trying to set screen margins following the guidelines for <a href="https://www.google.com/design/spec/layout/metrics-keylines.html" rel="noreferrer">Layout - Metrics and keylines</a>. Specifically, list content on mobile screens should have a margin of 72 dp and align with the title as shown in the guide:</p>
  
  <p><a href="https://i.stack.imgur.com/bSj4A.png" rel="noreferrer"><img src="https://i.stack.imgur.com/bSj4A.png" alt="enter image description here"></a></p>
  
  <p>As Android Studio automatically generates margin values in the res/dimens.xml, I thought that I'd get my content to align with the title by adding my own 'inner' margin:</p>
  
  <p><strong>dimens.xml</strong></p>
  
  <pre><code>&lt;resources&gt;
      &lt;!-- Default screen margins, per the Android Design guidelines. --&gt;
      &lt;dimen name="activity_horizontal_margin"&gt;16dp&lt;/dimen&gt;
      &lt;dimen name="activity_vertical_margin"&gt;16dp&lt;/dimen&gt;
  
      &lt;!-- 16 + 56 = 72 = "Content left margin from screen edge" --&gt;
      &lt;dimen name="content_horizontal_margin"&gt;56dp&lt;/dimen&gt;
  &lt;/resources&gt;
  </code></pre>
  
  <p><strong>myactivity.xml</strong></p>
  
  <pre><code>&lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
      android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
      android:paddingRight="@dimen/activity_horizontal_margin"&gt;
  
      &lt;TextView
          android:id="@+id/tvEditPlaylistInfo"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_alignParentLeft="true"
          android:layout_alignParentTop="true"
          android:layout_marginLeft="@dimen/content_horizontal_margin"
          android:textAppearance="?android:attr/textAppearanceMedium"
          android:text="test" /&gt;
  
      &lt;ImageButton
          android:layout_width="36dp"
          android:layout_height="36dp"
          android:src="@drawable/action_current"
          android:layout_alignBottom="@id/tvEditPlaylistInfo"
          android:layout_toRightOf="@id/tvEditPlaylistInfo"
          android:layout_marginLeft="16dp"/&gt;
  
      &lt;ListView
          android:id="@+id/lvAudioFiles"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:layout_marginLeft="@dimen/content_horizontal_margin"
          android:layout_below="@id/tvEditPlaylistInfo"&gt;
      &lt;/ListView&gt;
  
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>But somehow my content is "off" by about 8dp (emulator, Lollipop 22). </p>
  
  <p><a href="https://i.stack.imgur.com/qOS2w.png" rel="noreferrer"><img src="https://i.stack.imgur.com/qOS2w.png" alt="enter image description here"></a></p>
  
  <p>I'm using a custom theme with parent <code>Theme.AppCompat.Light.DarkActionBar</code> but I only changed colors so I think that is not the source of my problem.</p>
  
  <p>What am I missing?</p>