Improve time to texture destruction

Eliminate textureCache.mGarbage which is only cleared
in a trimMemory. Instead when we hit ~Bitmap post a
message to RenderThread to release the texture immediately

Bug: 38258699
Test: manual
Change-Id: I962ba275e89afb628ba02f74769287edbab9fed4
diff --git a/libs/hwui/renderthread/RenderProxy.h b/libs/hwui/renderthread/RenderProxy.h
index a60ed55..b21772c 100644
--- a/libs/hwui/renderthread/RenderProxy.h
+++ b/libs/hwui/renderthread/RenderProxy.h
@@ -135,6 +135,8 @@
     static sk_sp<Bitmap> allocateHardwareBitmap(SkBitmap& bitmap);
 
     static int copyGraphicBufferInto(GraphicBuffer* buffer, SkBitmap* bitmap);
+
+    static void onBitmapDestroyed(uint32_t pixelRefId);
 private:
     RenderThread& mRenderThread;
     CanvasContext* mContext;