Show snackbar with "undo" action when deleting group.

Bug 28955365
Bug 30223734
Change-Id: I16f175835815600e7fdb9d49794bb79002723ac0
diff --git a/res/layout/people_activity.xml b/res/layout/people_activity.xml
index d8b900d..9fd1a69 100644
--- a/res/layout/people_activity.xml
+++ b/res/layout/people_activity.xml
@@ -14,35 +14,43 @@
      limitations under the License.
 -->
 
-<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
-    android:id="@+id/list_container"
+<android.support.design.widget.CoordinatorLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/root"
     android:layout_width="match_parent"
-    android:layout_height="match_parent">
+    android:layout_height="match_parent" >
 
-    <!--
-        ViewPager for swiping between tabs.  We put fragments at runtime.
+    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+                    android:id="@+id/list_container"
+                    android:layout_width="match_parent"
+                    android:layout_height="match_parent">
 
-        (Adding them directly as the children of this view is not recommended.  ViewPager should
-        be treated like a ListView, which doesn't expect children to be added from the layout.)
-    -->
-    <android.support.v4.view.ViewPager
-        android:id="@+id/tab_pager"
-        android:layout_height="match_parent"
-        android:layout_width="match_parent"
-        android:layout_below="@id/toolbar_parent"
-        />
+        <!--
+            ViewPager for swiping between tabs.  We put fragments at runtime.
 
-    <FrameLayout
-        android:id="@+id/contacts_unavailable_view"
-        android:layout_width="match_parent"
-        android:layout_height="match_parent"
-        android:layout_below="@id/toolbar_parent"
-        android:visibility="gone">
-        <FrameLayout
-            android:id="@+id/contacts_unavailable_container"
+            (Adding them directly as the children of this view is not recommended.  ViewPager should
+            be treated like a ListView, which doesn't expect children to be added from the layout.)
+        -->
+        <android.support.v4.view.ViewPager
+            android:id="@+id/tab_pager"
             android:layout_height="match_parent"
-            android:layout_width="match_parent" />
-    </FrameLayout>
+            android:layout_width="match_parent"
+            android:layout_below="@id/toolbar_parent"
+            />
+
+        <FrameLayout
+            android:id="@+id/contacts_unavailable_view"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            android:layout_below="@id/toolbar_parent"
+            android:visibility="gone">
+            <FrameLayout
+                android:id="@+id/contacts_unavailable_container"
+                android:layout_height="match_parent"
+                android:layout_width="match_parent" />
+        </FrameLayout>
+
+    </RelativeLayout>
 
     <include layout="@layout/floating_action_button" />
-</RelativeLayout>
+</android.support.design.widget.CoordinatorLayout>
diff --git a/res/values/strings.xml b/res/values/strings.xml
index 9f1dd90..a40bce1 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -348,7 +348,7 @@
     <!-- Toast displayed when a label is saved [CHAR LIMIT=30] -->
     <string name="groupSavedToast">Label saved</string>
 
-    <!-- Toast displayed when a label name is deleted. [CHAR LIMIT=50] -->
+    <!-- Toast or snackbar displayed when a label name is deleted. [CHAR LIMIT=50] -->
     <string name="groupDeletedToast">Label deleted</string>
 
     <!-- Toast displayed when a new label name is created. [CHAR LIMIT=50] -->
@@ -964,6 +964,10 @@
     <!-- The body text for hamburger promo [CHAR LIMIT=200]-->
     <string name="hamburger_feature_highlight_body">Clean up duplicates &amp; group contacts by label</string>
 
+    <!-- The label for the action shown in a snackbar after an operation that modifies some data is performed.
+         The user can click on the action to rollback the modification-->
+    <string name="undo">Undo</string>
+
     <!-- Toast shown when text is copied to the clipboard [CHAR LIMIT=64] -->
     <string name="toast_text_copied">Text copied</string>
     <!-- Option displayed in context menu to copy long pressed item to clipboard [CHAR LIMIT=64] -->