Don't use framework strings for formatting file sizes

Modify various formatters to avoid using framework strings for
formatting file sizes.

Also update README instructions for running unit tests.

Bug: 36994779
Test: adb shell am instrument -w -e class com.android.settings.utils.FileSizeFormatterTest com.android.settings.tests.unit/android.support.test.runner.AndroidJUnitRunner
Test: make -j RunSettingsRoboTests
Change-Id: I4035f26d29408b64389892a4a2379b4823f8ac96

src/com/android/settings/deviceinfo/StorageItemPreference.java

@@ -18,6 +18,7 @@ package com.android.settings.deviceinfo;
 
 import android.content.Context;
 import android.content.res.Resources;
+import android.icu.util.MeasureUnit;
 import android.support.v7.preference.Preference;
 import android.support.v7.preference.PreferenceViewHolder;
 import android.util.AttributeSet;
@@ -51,7 +52,7 @@ public class StorageItemPreference extends Preference {
                 FileSizeFormatter.formatFileSize(
                         getContext(),
                         size,
-                        getGigabyteSuffix(getContext().getResources()),
+                        MeasureUnit.GIGABYTE,
                         FileSizeFormatter.GIGABYTE_IN_BYTES));
         if (total == 0) {
             mProgressPercent = 0;
@@ -75,8 +76,4 @@ public class StorageItemPreference extends Preference {
         updateProgressBar();
         super.onBindViewHolder(view);
     }
-
-    private static int getGigabyteSuffix(Resources res) {
-        return res.getIdentifier("gigabyteShort", "string", "android");
-    }
 }