Restore SystemProperties.PROP_NAME_MAX to keep Kindle running.

The limit has been lifted in O, but without this constant, Kindle crashes here:

  Caused by: java.lang.NoSuchFieldException: PROP_NAME_MAX
    at java.lang.Class.getField(Class.java:1607)
    at com.amazon.android.webkit.AmazonWebKitFactories$Implementation.<clinit>(AmazonWebKitFactories.java:59)

The code seems to want to truncate a system property name to avoid the
exception that SystemProperty.get threw if passed a name that was too long.

Bug: http://b/36095274
Test: select a word in Kindle
Change-Id: Id1881a8a7c6386400a1024beb0d1b741bdaefba7

core/java/android/os/SystemProperties.java

@@ -35,6 +35,12 @@ public class SystemProperties {
     private static final String TAG = "SystemProperties";
     private static final boolean TRACK_KEY_ACCESS = false;
 
+    /**
+     * Android O removed the property name length limit, but com.amazon.kindle 7.8.1.5
+     * uses reflection to read this whenever text is selected (http://b/36095274).
+     */
+    public static final int PROP_NAME_MAX = Integer.MAX_VALUE;
+
     public static final int PROP_VALUE_MAX = 91;
 
     private static final ArrayList<Runnable> sChangeCallbacks = new ArrayList<Runnable>();