Add a new module-only API to preload HttpEngine

This is supposed to be used only from the Zygote during the
initialization phase to preload HttpEngine. Currently, the
implementation only preloads a single class which is used to initialize
the backend for HttpEngine.

Bug: 380349437
Change-Id: If3ebcb37e51104a69473491e9f230d1b043c7bd0
diff --git a/framework/Android.bp b/framework/Android.bp
index 0334e11..4353213 100644
--- a/framework/Android.bp
+++ b/framework/Android.bp
@@ -156,6 +156,7 @@
 java_defaults {
     name: "CronetJavaDefaults",
     srcs: [":httpclient_api_sources"],
+    static_libs: ["com.android.net.http.flags-aconfig-java"],
     libs: [
         "androidx.annotation_annotation",
     ],
@@ -212,6 +213,7 @@
     },
     aconfig_declarations: [
         "com.android.net.flags-aconfig",
+        "com.android.net.http.flags-aconfig",
         "com.android.networksecurity.flags-aconfig",
     ],
 }