[vr] Disable optimized treewalks

Also removes some code leftover from debugging.

Bug: 832650
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_vr
Change-Id: I68271d0e97973b5dde393d6d1da3eaec32bd6259
Reviewed-on: https://chromium-review.googlesource.com/1012760Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Commit-Queue: Ian Vollick <vollick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550780}

chrome/browser/vr/elements/ui_element.cc

@@ -23,7 +23,7 @@ namespace vr {
 
 namespace {
 
-constexpr bool kEnableOptimizedTreeWalks = true;
+constexpr bool kEnableOptimizedTreeWalks = false;
 constexpr float kHitTestResolutionInMeter = 0.000001f;
 
 int AllocateId() {
@@ -257,7 +257,7 @@ bool UiElement::DoBeginFrame(const gfx::Transform& head_pose) {
                 updated_bindings_this_frame_) &&
                was_visible_at_any_point;
 
-  if (true || !kEnableOptimizedTreeWalks || was_visible_at_any_point ||
+  if (!kEnableOptimizedTreeWalks || was_visible_at_any_point ||
       visibility_bindings_depend_on_child_visibility_) {
     for (auto& child : children_)
       dirty |= child->DoBeginFrame(head_pose);