Always create top controls manager.

This CL removes the calculate_top_controls_position flag and instead
always creates the top controls manager. The methods of the manager
become no-ops if the top controls height is 0 so that it becomes
effectively enabled when a top controls height gets set.

This fixes the attached bug because some Android Chrome UI pages don't
have top controls but the manager was still created. These pages set
the height to 0 to hide the top controls but the methods of the
manager were still getting called. This caused a crash in Blink since
ScrollBy would try to calculate the shown ratio with a 0 height, causing
a NaN to propagate into Blink.

BUG=460007

Review URL: https://codereview.chromium.org/961023002

Cr-Commit-Position: refs/heads/master@{#319257}

1 files changed, 9 insertions, 0 deletions

diff --git a/cc/input/top_controls_manager.cc b/cc/input/top_controls_manager.cc
index 7362805..c8bd534 100644
--- a/cc/input/top_controls_manager.cc
+++ b/cc/input/top_controls_manager.cc
@@ -101,6 +101,9 @@ void TopControlsManager::ScrollBegin() {
 
 gfx::Vector2dF TopControlsManager::ScrollBy(
     const gfx::Vector2dF& pending_delta) {
+  if (!TopControlsHeight())
+    return pending_delta;
+
   if (pinch_gesture_active_)
     return pending_delta;
 
@@ -180,6 +183,12 @@ void TopControlsManager::SetupAnimation(AnimationDirection direction) {
   if (top_controls_animation_ && animation_direction_ == direction)
     return;
 
+  if (!TopControlsHeight()) {
+    client_->SetCurrentTopControlsShownRatio(
+        direction == HIDING_CONTROLS ? 0.f : 1.f);
+    return;
+  }
+
   top_controls_animation_ = KeyframedFloatAnimationCurve::Create();
   base::TimeDelta start_time = gfx::FrameTime::Now() - base::TimeTicks();
   top_controls_animation_->AddKeyframe(