Add KEY_VVM_PREFETCH_BOOLEAN to CarrierConfigManager

This key will allow the carrier to specify to prefetch audio data on
new voicemail arrival. The default value it true.

This setting is not available to the user because it add too much
complexity.

Bug:23945351
Change-Id: I5ca6b4f64c3818c5f37ba608f4ab450c8b0ed9dc
diff --git a/telephony/java/android/telephony/CarrierConfigManager.java b/telephony/java/android/telephony/CarrierConfigManager.java
index 320d274..56e081c 100644
--- a/telephony/java/android/telephony/CarrierConfigManager.java
+++ b/telephony/java/android/telephony/CarrierConfigManager.java
@@ -409,6 +409,11 @@
     public static final String KEY_VVM_CELLULAR_DATA_REQUIRED_BOOLEAN = "vvm_cellular_data_required";
 
     /**
+     * Whether to prefetch audio data on new voicemail arrival, defaulted to true.
+     */
+    public static final String KEY_VVM_PREFETCH_BOOLEAN = "vvm_prefetch";
+
+    /**
      * The package name of the carrier's visual voicemail app to ensure that dialer visual voicemail
      * and carrier visual voicemail are not active at the same time.
      */
@@ -638,6 +643,7 @@
         sDefaults.putInt(KEY_VVM_PORT_NUMBER_INT, 0);
         sDefaults.putString(KEY_VVM_TYPE_STRING, "");
         sDefaults.putBoolean(KEY_VVM_CELLULAR_DATA_REQUIRED_BOOLEAN,false);
+        sDefaults.putBoolean(KEY_VVM_PREFETCH_BOOLEAN,true);
         sDefaults.putString(KEY_CARRIER_VVM_PACKAGE_NAME_STRING, "");
         sDefaults.putBoolean(KEY_CI_ACTION_ON_SYS_UPDATE_BOOL, false);
         sDefaults.putString(KEY_CI_ACTION_ON_SYS_UPDATE_INTENT_STRING, "");