Update VR Button element's description

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: I913d26985c4fbe9ed1a9daea65ec57094aaf5043
Reviewed-on: https://chromium-review.googlesource.com/786327
Commit-Queue: David Dorwin <ddorwin@chromium.org>
Reviewed-by: Ian Vollick <vollick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521155}

chrome/browser/vr/elements/button.cc

@@ -137,11 +137,11 @@ void Button::NotifyClientSizeAnimated(const gfx::SizeF& size,
                                       cc::Animation* animation) {
   if (target_property_id == BOUNDS) {
     background_->SetSize(size.width(), size.height());
-    background_->set_corner_radius(size.width() * 0.5f);
+    background_->set_corner_radius(size.width() * 0.5f);  // Creates a circle.
     foreground_->SetSize(size.width() * kIconScaleFactor,
                          size.height() * kIconScaleFactor);
     hit_plane_->SetSize(size.width(), size.height());
-    hit_plane_->set_corner_radius(size.width() * 0.5f);
+    hit_plane_->set_corner_radius(size.width() * 0.5f);  // Creates a circle.
   }
   UiElement::NotifyClientSizeAnimated(size, target_property_id, animation);
 }

chrome/browser/vr/elements/button.h

@@ -24,8 +24,9 @@ namespace vr {
 class Rect;
 class VectorIcon;
 
-// Button has rounded rect as background and a vector icon as the foregroud.
+// Button has a circle as the background and a vector icon as the foreground.
 // When hovered, background and foreground both move forward on Z axis.
+// This matches the Daydream disk-style button.
 class Button : public UiElement {
  public:
   Button(base::Callback<void()> click_handler, const gfx::VectorIcon& icon);