Fix z-order for webview surface control

Set the root surface control transparent, and set the z order of the newly created child surface control to -1.
A new callback is needed to update root surface control in sync from Java side.

Bug: 186750329
Test: use latest APKs from Webview team, play a video, mini toolbar should be visible
Change-Id: I0b37ee8f83fd2b41ff4f2856dbadd31ff6170baf
diff --git a/libs/hwui/renderthread/RenderProxy.cpp b/libs/hwui/renderthread/RenderProxy.cpp
index 6fd644b..c47050c 100644
--- a/libs/hwui/renderthread/RenderProxy.cpp
+++ b/libs/hwui/renderthread/RenderProxy.cpp
@@ -319,6 +319,12 @@
             [this, cb = callback]() { mContext->setASurfaceTransactionCallback(cb); });
 }
 
+void RenderProxy::setPrepareSurfaceControlForWebviewCallback(
+        const std::function<void()>& callback) {
+    mRenderThread.queue().post(
+            [this, cb = callback]() { mContext->setPrepareSurfaceControlForWebviewCallback(cb); });
+}
+
 void RenderProxy::setFrameCallback(std::function<void(int64_t)>&& callback) {
     mDrawFrameTask.setFrameCallback(std::move(callback));
 }