sendDialerCode API review

address the feeback from API review:
throw exception rather than a boolean return.
handle exception from callers instead of check return boolean
move secret code detection logic from API to API callers.

Bug: 35767402
Test: Manual
Test: run cts -m CtsTelephonyTestCases -t android.telephony.cts.TelephonyManagerTest
Change-Id: Ie31f399799d4cd2413bf65a227fb000bbbe3c8aa
diff --git a/src/com/android/phone/SpecialCharSequenceMgr.java b/src/com/android/phone/SpecialCharSequenceMgr.java
index 2aa1043..3c02a30 100644
--- a/src/com/android/phone/SpecialCharSequenceMgr.java
+++ b/src/com/android/phone/SpecialCharSequenceMgr.java
@@ -151,8 +151,14 @@
      * @return true if a secret code was encountered and intent is sent out
      */
     static private boolean handleSecretCode(String input) {
-        Phone phone = PhoneGlobals.getPhone();
-        return phone.sendDialerCode(input);
+        // Secret codes are in the form *#*#<code>#*#*
+        int len = input.length();
+        if (len > 8 && input.startsWith("*#*#") && input.endsWith("#*#*")) {
+            final Phone phone = PhoneGlobals.getPhone();
+            phone.sendDialerSpecialCode(input.substring(4, len - 4));
+            return true;
+        }
+        return false;
     }
 
     static private boolean handleAdnEntry(Context context, String input) {