Revert "Revert "Add ExternalTexture class into RenderEngine inte..."

Revert submission 14199598-revert-14086921-renderengine-external-tex-QJNBWQMQEU

Reason for revert: Prepare for relanding
Reverted Changes:
I01e65a7f4:Revert "Update WaylandRenderSurface to accomodate ...
I7d58118c1:Revert "Update Readback VTS to align with RenderEn...
I1501890f4:Revert "Add ExternalTexture class into RenderEngin...

Added the following fixes:
1. CachedSet renders to intermediate texture variable rather than
mTexture directly, since mTexture is not guaranteed to be nonnull.
2. Add null check when setting new buffer in BLAST.

Bug: 185524947
Bug: 180767535
Test: builds, boots
Test: librenderengine_test
Change-Id: I52ea82e24336b496d996bbe3e445db0affe1abb8
diff --git a/libs/renderengine/ExternalTexture.cpp b/libs/renderengine/ExternalTexture.cpp
new file mode 100644
index 0000000..eabff58
--- /dev/null
+++ b/libs/renderengine/ExternalTexture.cpp
@@ -0,0 +1,43 @@
+/*
+ * Copyright 2021 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.
+ */
+
+#include <renderengine/ExternalTexture.h>
+#include <renderengine/RenderEngine.h>
+#include <ui/GraphicBuffer.h>
+
+#include "log/log_main.h"
+
+namespace android::renderengine {
+
+ExternalTexture::ExternalTexture(const sp<GraphicBuffer>& buffer, RenderEngine& renderEngine,
+                                 uint32_t usage)
+      : mBuffer(buffer), mRenderEngine(renderEngine) {
+    LOG_ALWAYS_FATAL_IF(buffer == nullptr,
+                        "Attempted to bind a null buffer to an external texture!");
+    // GLESRenderEngine has a separate texture cache for output buffers,
+    if (usage == Usage::WRITEABLE &&
+        (mRenderEngine.getRenderEngineType() == RenderEngine::RenderEngineType::GLES ||
+         mRenderEngine.getRenderEngineType() == RenderEngine::RenderEngineType::THREADED)) {
+        return;
+    }
+    mRenderEngine.mapExternalTextureBuffer(mBuffer, usage & Usage::WRITEABLE);
+}
+
+ExternalTexture::~ExternalTexture() {
+    mRenderEngine.unmapExternalTextureBuffer(mBuffer);
+}
+
+} // namespace android::renderengine