Use local origin of an element to calculate element bounds

(0, 0) was always an element center previously. But with the concept of
local_origin for an element introduced, this is no longer true. This CL uses
(local_origin, 0) instead of using (0, 0, 0) when construct an element's
bound.

Bug: NONE
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: If5b03f0c0a0a4329ce19ecc1a465469f57d77983
Reviewed-on: https://chromium-review.googlesource.com/779560
Commit-Queue: Biao She <bshe@chromium.org>
Reviewed-by: Ian Vollick <vollick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#517917}

chrome/browser/vr/elements/ui_element.cc

@@ -460,7 +460,7 @@ void UiElement::DoLayOutChildren() {
     if (!child->IsVisible()) {
       continue;
     }
-    gfx::Point3F child_center;
+    gfx::Point3F child_center(child->local_origin());
     child->LocalTransform().TransformPoint(&child_center);
     gfx::RectF local_rect =
         gfx::RectF(child_center.x() - 0.5 * child->size().width(),

chrome/browser/vr/elements/ui_element_unittest.cc

@@ -64,6 +64,16 @@ TEST(UiElement, BoundsContainChildren) {
   parent->DoLayOutChildren();
   EXPECT_RECT_NEAR(gfx::RectF(-0.5f, 0.5f, 9.2f, 7.4f),
                    gfx::RectF(parent->local_origin(), parent->size()), epsilon);
+
+  auto grand_parent = base::MakeUnique<UiElement>();
+  grand_parent->set_bounds_contain_children(true);
+  grand_parent->set_padding(0.1, 0.2);
+  grand_parent->AddChild(std::move(parent));
+
+  grand_parent->DoLayOutChildren();
+  EXPECT_RECT_NEAR(
+      gfx::RectF(-0.5f, 0.5f, 9.4f, 7.8f),
+      gfx::RectF(grand_parent->local_origin(), grand_parent->size()), epsilon);
 }
 
 TEST(UiElements, AnimateSize) {