title: Collapsed Toolbar Title is not centered when setDisplayHomeAsUpEnabled is true
body: <p>I am using a <code>CollapsingToolbarLayout</code> and when it collapses, the title is not in the middle due to the space occupied by the back button as I set <code>setDisplayHomeAsUpEnabled</code> to true. Any way to fix this?</p>
  
  <p>Take note that I am <strong>NOT</strong> using a separate <code>TextView</code> for the title, instead I am using the <code>CollapsingToolbarLayout</code>'s <code>title</code> attribute.</p>
  
  <p><a href="https://i.stack.imgur.com/YybSI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YybSI.png" alt="enter image description here"></a></p>
  
  <p>Here is my XML:</p>
  
  <pre><code>    &lt;android.support.design.widget.AppBarLayout
      android:id="@+id/appbar"
      android:layout_width="match_parent"
      android:layout_height="300dp"
      android:fitsSystemWindows="true"&gt;
  
      &lt;android.support.design.widget.CollapsingToolbarLayout
          android:id="@+id/collapsing_toolbar"
          android:layout_width="match_parent"
          android:layout_height="match_parent"
          android:layout_gravity="center"
          android:fitsSystemWindows="true"
          app:collapsedTitleGravity="center_horizontal"
          app:contentScrim="@color/main_orange"
          app:expandedTitleMarginBottom="75dp"
          app:expandedTitleMarginEnd="64dp"
          app:expandedTitleMarginStart="10dp"
          app:expandedTitleTextAppearance="@style/CollapsibleToolbarTitleTextAppearanceExpanded"
          app:layout_scrollFlags="scroll|exitUntilCollapsed"&gt;
  
          &lt;RelativeLayout
              android:layout_width="match_parent"
              android:layout_height="match_parent"
              android:fitsSystemWindows="true"&gt;
  
              &lt;LinearLayout
                  android:layout_width="wrap_content"
                  android:layout_height="wrap_content"
                  android:layout_centerInParent="true"
                  android:layout_margin="5dp"
                  android:orientation="vertical"&gt;
  
                  &lt;ImageView
                      android:layout_width="wrap_content"
                      android:layout_height="wrap_content"
                      android:layout_gravity="center"
                      android:src="@drawable/ic_image_area_black_48dp"
                      android:tint="@color/white_50" /&gt;
  
                  &lt;TextView
                      android:id="@+id/failedToLoadImageText"
                      android:layout_width="wrap_content"
                      android:layout_height="wrap_content"
                      android:layout_gravity="center_vertical"
                      android:layout_marginTop="10dp"
                      android:gravity="center"
                      android:shadowColor="@color/black"
                      android:shadowRadius="3"
                      android:text="Please connect to the internet to view the photo"
                      android:textColor="@color/white_50" /&gt;
              &lt;/LinearLayout&gt;
  
              &lt;android.support.v4.view.ViewPager
                  android:id="@+id/galleryViewPager"
                  android:layout_width="match_parent"
                  android:layout_height="match_parent" /&gt;
  
              &lt;ImageView
                  android:layout_width="match_parent"
                  android:layout_height="150dp"
                  android:layout_alignParentBottom="true"
                  android:layout_centerVertical="true"
                  android:background="@drawable/black_gradient"
                  android:fitsSystemWindows="true"
                  android:scaleType="centerCrop"
                  app:layout_collapseMode="parallax" /&gt;
  
          &lt;/RelativeLayout&gt;
  
          &lt;TextView
              android:id="@+id/subtitle"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_gravity="bottom"
              android:layout_marginBottom="30dp"
              android:layout_marginEnd="10dp"
              android:layout_marginStart="10dp"
              android:maxLines="2"
              android:text="Lorem Ipsum Iran Lorem Ipsum Iran Lorem Ipsum Iran Lorem Ipsum Iran Lorem Ipsum Iran Lorem Ipsum Iran Lorem Ipsum Iran Lorem Ipsum Iran "
              android:textColor="@android:color/white"
              android:textSize="16sp"
              app:layout_collapseMode="parallax" /&gt;
  
          &lt;com.rd.PageIndicatorView
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_gravity="center|bottom"
              android:layout_marginBottom="10dp"
              app:layout_collapseMode="parallax"
              app:piv_radius="5dp"
              app:piv_selectedColor="@color/main_orange"
              app:piv_unselectedColor="@color/dim_gray_50"
              app:piv_viewPager="@id/galleryViewPager" /&gt;
  
          &lt;android.support.v7.widget.Toolbar
              android:id="@+id/toolbar"
              android:layout_width="match_parent"
              android:layout_height="?attr/actionBarSize"
              app:contentInsetEnd="0dp"
              app:contentInsetLeft="0dp"
              app:contentInsetRight="0dp"
              app:contentInsetStart="0dp"
              app:contentInsetStartWithNavigation="0dp"
              app:layout_collapseMode="pin"
              app:popupTheme="@style/ThemeOverlay.AppCompat.Light"&gt;
          &lt;/android.support.v7.widget.Toolbar&gt;
      &lt;/android.support.design.widget.CollapsingToolbarLayout&gt;
  &lt;/android.support.design.widget.AppBarLayout&gt;
  </code></pre>