Defer deleting ExternalTextures that go out of scope during DrawLayers

Some buffers (e.g. protected content) are not pre-mapped into a
texture.  Their textures are created in drawLayers and go out of scope
at the end of drawLayers drawLayers when those temporary textures are
sent to the GPU.

This CL ensures that in those cases we defer unbinding and deleting the
temporary texture until the cleanupPostRender method is called. Also to
avoid unecessary thread hops into cleanupPostRender this CL also adds a
thread-safe check to see if cleanup is necessary. Finally, we also make
the threaded variant asynchronous to further improve the availability of
SurfaceFlinger.

Bug: 190628682
Bug: 191132989
Test: atest librenderengine_test and perfetto traces
Change-Id: Ic2f4384cd1957c928a0ef656a98eb0041e29622c
diff --git a/libs/renderengine/threaded/RenderEngineThreaded.h b/libs/renderengine/threaded/RenderEngineThreaded.h
index c81f137..9b523b2 100644
--- a/libs/renderengine/threaded/RenderEngineThreaded.h
+++ b/libs/renderengine/threaded/RenderEngineThreaded.h
@@ -54,7 +54,7 @@
     bool isProtected() const override;
     bool supportsProtectedContent() const override;
     bool useProtectedContext(bool useProtectedContext) override;
-    bool cleanupPostRender(CleanupMode mode) override;
+    void cleanupPostRender() override;
 
     status_t drawLayers(const DisplaySettings& display,
                         const std::vector<const LayerSettings*>& layers,
@@ -70,6 +70,7 @@
 protected:
     void mapExternalTextureBuffer(const sp<GraphicBuffer>& buffer, bool isRenderable) override;
     void unmapExternalTextureBuffer(const sp<GraphicBuffer>& buffer) override;
+    bool canSkipPostRenderCleanup() const override;
 
 private:
     void threadMain(CreateInstanceFactory factory);