Add back render-ahead support

Currently only supported in the EGL path.
Vulkan support Coming Soon

Bug: 127822449
Test: trace of hwuimacro
Change-Id: Iac2b039e11d964aab5b8ca1bdf2a5430b187e2ea
diff --git a/libs/hwui/Properties.h b/libs/hwui/Properties.h
index 0a7f4e7..3e91c63 100644
--- a/libs/hwui/Properties.h
+++ b/libs/hwui/Properties.h
@@ -167,6 +167,8 @@
 
 #define PROPERTY_ENABLE_FORCE_DARK "debug.hwui.force_dark_enabled"
 
+#define PROPERTY_RENDERAHEAD "debug.hwui.render_ahead"
+
 ///////////////////////////////////////////////////////////////////////////////
 // Misc
 ///////////////////////////////////////////////////////////////////////////////
@@ -251,6 +253,8 @@
 
     ANDROID_API static int contextPriority;
 
+    static int defaultRenderAhead;
+
 private:
     static ProfileType sProfileType;
     static bool sDisableProfileBars;