Provide a preference to delete data from cloud.

For now, it is a debug preference, but we may make this a proper
user setting in the future. Thus note that the messaging is not
final.

Pref looks like :
1. https://screenshot.googleplex.com/OLxW0myWD9.png
2. https://screenshot.googleplex.com/YeqWYXGstw.png

Bug: 18106936
Change-Id: I88bbc1a2ee0c23a48ff3972a91d57c218b10bb65
diff --git a/java/res/values/strings.xml b/java/res/values/strings.xml
index e1a72c4..5eaac09 100644
--- a/java/res/values/strings.xml
+++ b/java/res/values/strings.xml
@@ -61,6 +61,11 @@
     <string name="cloud_sync_summary" translatable="false">Sync your personal dictionary across devices</string>
     <string name="cloud_sync_summary_disabled_signed_out" translatable="false">Select an account to enable sync</string>
     <string name="sync_now_title" translatable="false">[DEBUG] Sync Now</string>
+    <string name="clear_sync_data_title" translatable="false">[DEBUG] Delete Google Keyboard cloud data</string>
+    <string name="clear_sync_data_summary" translable="false">Deletes your synced data from Google</string>
+    <string name="clear_sync_data_confirmation" translable="false">Your synced data will be deleted. Are you sure?</string>
+    <string name="clear_sync_data_ok" translable="false">Delete</string>
+    <string name="clear_sync_data_cancel" translable="false">Cancel</string>
 
     <!-- Option name for including other IMEs in the language switch list [CHAR LIMIT=30] -->
     <string name="include_other_imes_in_language_switch_list">Switch to other input methods</string>
diff --git a/java/res/xml/prefs_screen_accounts.xml b/java/res/xml/prefs_screen_accounts.xml
index 41642bf..4624885 100644
--- a/java/res/xml/prefs_screen_accounts.xml
+++ b/java/res/xml/prefs_screen_accounts.xml
@@ -48,4 +48,11 @@
         android:persistent="false"
         android:title="@string/sync_now_title"
         android:dependency="pref_enable_cloud_sync" />
+
+    <!-- This preference (acts like a button) enables the user to clear data from the cloud. -->
+    <Preference android:key="pref_beanstalk_clear_data"
+        android:persistent="false"
+        android:title="@string/clear_sync_data_title"
+        android:summary="@string/clear_sync_data_summary"
+        android:dependency="pref_enable_cloud_sync" />
 </PreferenceScreen>