Add Swappy & Pre-Transformed Swapchain

- Adds Swappy for Android for stable frame pacing
- Implements pre-transformed Swapchain so that Godot's compositor is in
charge of rotating the screen instead of Android's compositor
(performance optimization for phones that don't have HW rotator)

============================

The work was performed by collaboration of TheForge and Google. I am
merely splitting it up into smaller PRs and cleaning it up.

Changes from original PR:

- Removed "display/window/frame_pacing/android/target_frame_rate" option
to use Engine::get_max_fps instead.
- Target framerate can be changed at runtime using Engine::set_max_fps.
- Swappy is enabled by default.
- Added documentation.
- enable_auto_swap setting is replaced with swappy_mode.

1 files changed, 41 insertions, 0 deletions

diff --git a/thirdparty/swappy-frame-pacing/common/gamesdk_common.h b/thirdparty/swappy-frame-pacing/common/gamesdk_common.h
new file mode 100644
index 0000000000..d29ac01af3
--- /dev/null
+++ b/thirdparty/swappy-frame-pacing/common/gamesdk_common.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * This is the main interface to the Android Performance Tuner library, also
+ * known as Tuning Fork.
+ *
+ * It is part of the Android Games SDK and produces best results when integrated
+ * with the Swappy Frame Pacing Library.
+ *
+ * See the documentation at
+ * https://developer.android.com/games/sdk/performance-tuner/custom-engine for
+ * more information on using this library in a native Android game.
+ *
+ */
+
+#pragma once
+
+// There are separate versions for each GameSDK component that use this format:
+#define ANDROID_GAMESDK_PACKED_VERSION(MAJOR, MINOR, BUGFIX) \
+    ((MAJOR << 16) | (MINOR << 8) | (BUGFIX))
+// Accessors
+#define ANDROID_GAMESDK_MAJOR_VERSION(PACKED) ((PACKED) >> 16)
+#define ANDROID_GAMESDK_MINOR_VERSION(PACKED) (((PACKED) >> 8) & 0xff)
+#define ANDROID_GAMESDK_BUGFIX_VERSION(PACKED) ((PACKED) & 0xff)
+
+#define AGDK_STRING_VERSION(MAJOR, MINOR, BUGFIX, GIT) \
+#MAJOR "." #MINOR "." #BUGFIX "." #GIT