Document that stopPreview is not needed before takePicture.

Also, applications can call startPreview after jpeg callback is received.

http://b/2292461
diff --git a/core/java/android/hardware/Camera.java b/core/java/android/hardware/Camera.java
index 4b733ef..ac159f4 100644
--- a/core/java/android/hardware/Camera.java
+++ b/core/java/android/hardware/Camera.java
@@ -477,6 +477,10 @@
      * application does not need a particular callback, a null can be passed
      * instead of a callback method.
      *
+     * This method will stop the preview. Applications should not call {@link
+     * #stopPreview()} before this. After jpeg callback is received,
+     * applications can call {@link #startPreview()} to restart the preview.
+     *
      * @param shutter   callback after the image is captured, may be null
      * @param raw       callback with raw image data, may be null
      * @param jpeg      callback with jpeg image data, may be null
@@ -500,6 +504,10 @@
      * application does not need a particular callback, a null can be passed
      * instead of a callback method.
      *
+     * This method will stop the preview. Applications should not call {@link
+     * #stopPreview()} before this. After jpeg callback is received,
+     * applications can call {@link #startPreview()} to restart the preview.
+     *
      * @param shutter   callback after the image is captured, may be null
      * @param raw       callback with raw image data, may be null
      * @param postview  callback with postview image data, may be null