Add experimental camera session prepare API.

Bug: 18949148
Change-Id: I8f73e68ea2e3acc60d98954106f364d13f439a82
diff --git a/camera/camera2/ICameraDeviceUser.cpp b/camera/camera2/ICameraDeviceUser.cpp
index d2dc200..2a9fd2b 100644
--- a/camera/camera2/ICameraDeviceUser.cpp
+++ b/camera/camera2/ICameraDeviceUser.cpp
@@ -49,7 +49,8 @@
     WAIT_UNTIL_IDLE,
     FLUSH,
     PREPARE,
-    TEAR_DOWN
+    TEAR_DOWN,
+    PREPARE2
 };
 
 namespace {
@@ -366,6 +367,21 @@
         return reply.readInt32();
     }
 
+    virtual status_t prepare2(int maxCount, int streamId)
+    {
+        ALOGV("prepare2");
+        Parcel data, reply;
+
+        data.writeInterfaceToken(ICameraDeviceUser::getInterfaceDescriptor());
+        data.writeInt32(maxCount);
+        data.writeInt32(streamId);
+
+        remote()->transact(PREPARE2, data, &reply);
+
+        reply.readExceptionCode();
+        return reply.readInt32();
+    }
+
     virtual status_t tearDown(int streamId)
     {
         ALOGV("tearDown");
@@ -592,7 +608,14 @@
             reply->writeInt32(tearDown(streamId));
             return NO_ERROR;
         } break;
-
+        case PREPARE2: {
+            CHECK_INTERFACE(ICameraDeviceUser, data, reply);
+            int maxCount = data.readInt32();
+            int streamId = data.readInt32();
+            reply->writeNoException();
+            reply->writeInt32(prepare2(maxCount, streamId));
+            return NO_ERROR;
+        } break;
         default:
             return BBinder::onTransact(code, data, reply, flags);
     }