Final structural tweaks to Telecomm API (1/8)

Bug: 16416927
Bug: 16494880
Change-Id: I45fbe287c410cbb5e1b985f320b862d732811f43
diff --git a/telecomm/java/android/telecomm/PhoneAccountHandle.java b/telecomm/java/android/telecomm/PhoneAccountHandle.java
index f14766c..04cd2b0 100644
--- a/telecomm/java/android/telecomm/PhoneAccountHandle.java
+++ b/telecomm/java/android/telecomm/PhoneAccountHandle.java
@@ -23,8 +23,7 @@
 import java.util.Objects;
 
 /**
- * Represents a distinct account, line of service or call placement method that
- * the system can use to place phone calls.
+ * The unique identifier for a {@link PhoneAccount}.
  */
 public class PhoneAccountHandle implements Parcelable {
     private ComponentName mComponentName;
@@ -48,10 +47,18 @@
     }
 
     /**
-     * A unique identifier for this {@code PhoneAccountHandle}, generated by and meaningful to the
-     * {@link android.telecomm.ConnectionService} that created it.
+     * A string that uniquely distinguishes this particular {@code PhoneAccountHandle} from all the
+     * others supported by the {@link ConnectionService} that created it.
+     * <p>
+     * A {@code ConnectionService} must select identifiers that are stable for the lifetime of
+     * their users' relationship with their service, across many Android devices. For example, a
+     * good set of identifiers might be the email addresses with which with users registered for
+     * their accounts with a particular service. Depending on how a service chooses to operate,
+     * a bad set of identifiers might be an increasing series of integers
+     * ({@code 0}, {@code 1}, {@code 2}, ...) that are generated locally on each phone and could
+     * collide with values generated on other phones or after a data wipe of a given phone.
      *
-     * @return A unique identifier for this {@code PhoneAccountHandle}.
+     * @return A service-specific unique identifier for this {@code PhoneAccountHandle}.
      */
     public String getId() {
         return mId;