Add Data warning and limit footer text.

Bug: 70550124
Test: XML only change, visual inspection.
Change-Id: Iaea3f100051bb908b13ca6809463db7f01f8d92d

res/values/strings.xml

@@ -8687,6 +8687,9 @@
     <!-- Label for button to set the amount of data before user is warned about usage [CHAR LIMIT=30] -->
     <string name="data_warning">Data warning</string>
 
+    <!-- Label for footnote on Data warning and limit page to warn of device discrepancies -->
+    <string name="data_warning_footnote">Data warning and data limit are measured by your device. This may be different from carrier data.</string>
+
     <!-- Label for switch about whether to limit how much data can be used [CHAR LIMIT=30] -->
     <string name="set_data_limit">Set data limit</string>
 

src/com/android/settings/datausage/BillingCycleSettings.java

@@ -91,6 +91,8 @@ public class BillingCycleSettings extends DataUsageBase implements
         mEnableDataLimit = (SwitchPreference) findPreference(KEY_SET_DATA_LIMIT);
         mEnableDataLimit.setOnPreferenceChangeListener(this);
         mDataLimit = findPreference(KEY_DATA_LIMIT);
+
+        mFooterPreferenceMixin.createFooterPreference().setTitle(R.string.data_warning_footnote);
     }
 
     @Override