Camera2: Add prepare for output streams

The prepare call asynchronously pre-allocates buffers for a given
output stream, and then fires the onPrepared callback.

Not implemented for Camera2Device or used in Camera2Client.

Change-Id: I1cccdfff846dd6985133c591dbdceed823929ade
diff --git a/services/camera/libcameraservice/common/Camera2ClientBase.cpp b/services/camera/libcameraservice/common/Camera2ClientBase.cpp
index c0c2314..ba0b264 100644
--- a/services/camera/libcameraservice/common/Camera2ClientBase.cpp
+++ b/services/camera/libcameraservice/common/Camera2ClientBase.cpp
@@ -280,6 +280,14 @@
 }
 
 template <typename TClientBase>
+void Camera2ClientBase<TClientBase>::notifyPrepared(int streamId) {
+    (void)streamId;
+
+    ALOGV("%s: Stream %d now prepared",
+            __FUNCTION__, streamId);
+}
+
+template <typename TClientBase>
 int Camera2ClientBase<TClientBase>::getCameraId() const {
     return TClientBase::mCameraId;
 }