Addressing comments in 74bdd21.

Change-Id: I807733dabc18bc8894c777d19c4d0e3ca809476c

Author: sganov

core/res/res/layout-port/keyguard_host_view.xml

@@ -69,8 +69,8 @@
         </com.android.internal.policy.impl.keyguard.KeyguardSecurityContainer>
 
         <ImageButton
-              android:layout_width="wrap_content"
-              android:layout_height="wrap_content"
+              android:layout_width="match_parent"
+              android:layout_height="@dimen/kg_widget_pager_bottom_padding"
               androidprv:layout_childType="expandChallengeHandle"
               android:focusable="true"
               android:background="@null"

policy/src/com/android/internal/policy/impl/keyguard/SlidingChallengeLayout.java

@@ -891,7 +891,12 @@ protected void onLayout(boolean changed, int l, int t, int r, int b) {
                 child.setAlpha(getChallengeAlpha());
                 child.layout(left, bottom - childHeight, left + childWidth, bottom);
             } else if (lp.childType == LayoutParams.CHILD_TYPE_EXPAND_CHALLENGE_HANDLE) {
-                child.layout(0, b - mChallengeBottomBound, width, b);
+                final int center = (paddingLeft + width - paddingRight) / 2;
+                final int left = center - child.getMeasuredWidth() / 2;
+                final int right = left + child.getMeasuredWidth();
+                final int bottom = height - paddingBottom - lp.bottomMargin;
+                final int top = bottom - child.getMeasuredHeight();
+                child.layout(left, top, right, bottom);
             } else {
                 // Non-challenge views lay out from the upper left, layered.
                 child.layout(paddingLeft + lp.leftMargin,