Expose GSM Timing Advance, Update LTE TA docstring

-Expose the GSM timing advance
-Add a spec reference to the LTE Timing Advance

Bug: 28910982
Test: None
Change-Id: I7573dbb1316a2ab52051072ebad2532601f4299c
diff --git a/api/current.txt b/api/current.txt
index 9cfbbc7..bbbca7f 100644
--- a/api/current.txt
+++ b/api/current.txt
@@ -36855,6 +36855,7 @@
     method public int getAsuLevel();
     method public int getDbm();
     method public int getLevel();
+    method public int getTimingAdvance();
     method public int hashCode();
     method public void writeToParcel(android.os.Parcel, int);
     field public static final android.os.Parcelable.Creator<android.telephony.CellSignalStrengthGsm> CREATOR;
diff --git a/api/system-current.txt b/api/system-current.txt
index fab5e00..798c420 100644
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -39790,6 +39790,7 @@
     method public int getAsuLevel();
     method public int getDbm();
     method public int getLevel();
+    method public int getTimingAdvance();
     method public int hashCode();
     method public void writeToParcel(android.os.Parcel, int);
     field public static final android.os.Parcelable.Creator<android.telephony.CellSignalStrengthGsm> CREATOR;
diff --git a/api/test-current.txt b/api/test-current.txt
index 7a58e1e..2609e52 100644
--- a/api/test-current.txt
+++ b/api/test-current.txt
@@ -36932,6 +36932,7 @@
     method public int getAsuLevel();
     method public int getDbm();
     method public int getLevel();
+    method public int getTimingAdvance();
     method public int hashCode();
     method public void writeToParcel(android.os.Parcel, int);
     field public static final android.os.Parcelable.Creator<android.telephony.CellSignalStrengthGsm> CREATOR;
diff --git a/telephony/java/android/telephony/CellSignalStrengthGsm.java b/telephony/java/android/telephony/CellSignalStrengthGsm.java
index addf7ef..4137853 100644
--- a/telephony/java/android/telephony/CellSignalStrengthGsm.java
+++ b/telephony/java/android/telephony/CellSignalStrengthGsm.java
@@ -141,6 +141,16 @@
     }
 
     /**
+     * Get the GSM timing advance between 0..219 symbols (normally 0..63).
+     * Integer.MAX_VALUE is reported when there is no RR connection.
+     * Refer to 3GPP 45.010 Sec 5.8
+     * @return the current GSM timing advance, if available.
+     */
+    public int getTimingAdvance() {
+        return mTimingAdvance;
+    }
+
+    /**
      * Get the signal strength as dBm
      */
     @Override
diff --git a/telephony/java/android/telephony/CellSignalStrengthLte.java b/telephony/java/android/telephony/CellSignalStrengthLte.java
index 3c0a8d6..bc8c85c8 100644
--- a/telephony/java/android/telephony/CellSignalStrengthLte.java
+++ b/telephony/java/android/telephony/CellSignalStrengthLte.java
@@ -206,8 +206,10 @@
     }
 
     /**
-     * Get the timing advance value for LTE.
-     * See 3GPP xxxx
+     * Get the timing advance value for LTE, as a value between 0..63.
+     * Integer.MAX_VALUE is reported when there is no active RRC
+     * connection. Refer to 3GPP 36.213 Sec 4.2.3
+     * @return the LTE timing advance, if available.
      */
     public int getTimingAdvance() {
         return mTimingAdvance;