Use TextUtils.substring instead of String.substring.
Use TextUtils.substring instead of String.substring.

This is a small refactoring of using substring method.
Calling TextUtils.substring is more efficient than calling
toString and String.substring.

Change-Id: I0a740b2a2fdbfb6b6155c4e926e17889025082f5

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base