Add detailed Skia traces sysprop to RenderEngine.

BUG:180767647
Test: setprop, force client composition, perfetto trace

1. `adb shell setprop debug.renderengine.skia_atrace_enabled 1`
2. `adb shell stop && adb shell start`
3. Force client composition:
   `adb shell service call SurfaceFlinger 1008 i32 1`
   (`adb shell dumpsys SurfaceFlinger | grep -A 30 "HWC layers"` can
   be used to check layers are "CLIENT" instead of "DEVICE".)
4. Perfetto script to trace.
5. See skia traces e.g. `grsurfacedrawcontext` in surfaceflinger
RenderEngine process.

Change-Id: I0612e3df82de08ab6a754b4f60d09057d335b1b1
diff --git a/libs/renderengine/skia/SkiaRenderEngine.h b/libs/renderengine/skia/SkiaRenderEngine.h
index 308c5ff..7bb6d6d 100644
--- a/libs/renderengine/skia/SkiaRenderEngine.h
+++ b/libs/renderengine/skia/SkiaRenderEngine.h
@@ -36,7 +36,7 @@
 class SkiaRenderEngine : public RenderEngine {
 public:
     static std::unique_ptr<SkiaRenderEngine> create(const RenderEngineCreationArgs& args);
-    SkiaRenderEngine(RenderEngineType type) : RenderEngine(type) {}
+    SkiaRenderEngine(RenderEngineType type);
     ~SkiaRenderEngine() override {}
 
     virtual void primeCache() override{};
@@ -60,8 +60,8 @@
 
 protected:
     virtual void mapExternalTextureBuffer(const sp<GraphicBuffer>& /*buffer*/,
-                                          bool /*isRenderable*/) override;
-    virtual void unmapExternalTextureBuffer(const sp<GraphicBuffer>& /*buffer*/) override;
+                                          bool /*isRenderable*/) override = 0;
+    virtual void unmapExternalTextureBuffer(const sp<GraphicBuffer>& /*buffer*/) override = 0;
 };
 
 } // namespace skia