Implement new compositor and ContentViewCore reparenting for VR Shell.

chrome/browser/android/vr_shell/vr_compositor.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/android/vr_shell/vr_compositor.h"
+
+#include "cc/layers/layer.h"
+#include "content/public/browser/android/compositor.h"
+#include "content/public/browser/android/content_view_core.h"
+#include "content/public/browser/web_contents.h"
+#include "ui/android/window_android.h"
+
+namespace vr_shell {
+
+VrCompositor::VrCompositor(ui::WindowAndroid* window) {
+  compositor_.reset(content::Compositor::Create(this, window));
+}
+
+VrCompositor::~VrCompositor() {
+  if (layer_parent_ && layer_) {
+    layer_parent_->AddChild(layer_);
+  }
+}
+
+void VrCompositor::UpdateLayerTreeHost() {}
+
+void VrCompositor::OnSwapBuffersCompleted(int pending_swap_buffers) {}
+
+void VrCompositor::SetLayer(content::ContentViewCore* core) {

[mdjones, 2016/09/20 20:29:44]

Will this ever be called more than once for this object? If so, the reparenting
logic should be somewhere other than the destructor.

[mthiesse, 2016/09/20 20:56:08]

This will only ever be called once. I've added an assert to ensure this.

+  ui::ViewAndroid* view_android = core->GetWebContents()->GetNativeView();
+  // When we pass the layer for the ContentViewCore to the compositor it may be
+  // removing it from its previous parent, so we remember that and restore it to
+  // its previous parent on teardown.
+  layer_ = view_android->GetLayer();
+  layer_parent_ = layer_->parent();
+  compositor_->SetRootLayer(view_android->GetLayer());
+}
+
+void VrCompositor::SurfaceDestroyed() {
+  compositor_->SetSurface(nullptr);
+}
+
+void VrCompositor::SurfaceChanged(
+    int width,
+    int height,
+    const base::android::JavaParamRef<jobject>& surface) {
+  DCHECK(surface);
+  compositor_->SetSurface(surface);
+  compositor_->SetWindowBounds(gfx::Size(width, height));
+}
+
+}  // namespace vr_shell