Add thread safety documentation

An upcoming change will remove "synchronized" from the API docs. This change
documents those cases where the guarantees can be determined from code
inspection.

Bug: 25767152
Change-Id: I75083ce01513ed315222304fe3f34190d40748cb

core/java/android/bluetooth/BluetoothAdapter.java

@@ -74,6 +74,8 @@ import java.util.UUID;
  * {@link #listenUsingRfcommWithServiceRecord(String,UUID)}; or start a scan for
  * Bluetooth LE devices with {@link #startLeScan(LeScanCallback callback)}.
  *
+ * <p>This class is thread safe.
+ *
  * <p class="note"><strong>Note:</strong>
  * Most methods require the {@link android.Manifest.permission#BLUETOOTH}
  * permission and some also require the
@@ -82,7 +84,7 @@ import java.util.UUID;
  * <div class="special reference">
  * <h3>Developer Guides</h3>
  * <p>For more information about using Bluetooth, read the
- * <a href="{@docRoot}guide/topics/wireless/bluetooth.html">Bluetooth</a> developer guide.</p>
+ * <a href="{@docRoot}guide/topics/wireless/bluetooth.html">Bluetooth</a> developer guide.
  * </div>
  *
  * {@see BluetoothDevice}

core/java/android/net/LocalSocket.java

@@ -25,7 +25,8 @@ import java.net.SocketOptions;
 
 /**
  * Creates a (non-server) socket in the UNIX-domain namespace. The interface
- * here is not entirely unlike that of java.net.Socket
+ * here is not entirely unlike that of java.net.Socket. This class and the streams
+ * returned from it may be used from multiple threads.
  */
 public class LocalSocket implements Closeable {
 

core/java/android/net/http/HttpResponseCache.java

@@ -36,7 +36,8 @@ import java.util.Map;
  * saving time and bandwidth. This class supports {@link
  * java.net.HttpURLConnection} and {@link javax.net.ssl.HttpsURLConnection};
  * there is no platform-provided cache for {@code DefaultHttpClient} or
- * {@code AndroidHttpClient}.
+ * {@code AndroidHttpClient}. Installation and instances are thread
+ * safe.
  *
  * <h3>Installing an HTTP response cache</h3>
  * Enable caching of all of your application's HTTP requests by installing the

core/java/android/util/EventLog.java

@@ -52,7 +52,7 @@ public class EventLog {
     private static HashMap<String, Integer> sTagCodes = null;
     private static HashMap<Integer, String> sTagNames = null;
 
-    /** A previously logged event read from the logs. */
+    /** A previously logged event read from the logs. Instances are thread safe. */
     public static final class Event {
         private final ByteBuffer mBuffer;
 

media/java/android/media/MediaMetadataEditor.java

@@ -73,7 +73,8 @@ import android.util.SparseIntArray;
 
     /**
      * Applies all of the metadata changes that have been set since the MediaMetadataEditor instance
-     * was created or since {@link #clear()} was called.
+     * was created or since {@link #clear()} was called. Subclasses should synchronize on
+     * {@code this} for thread safety.
      */
     public abstract void apply();