Simplify ToolbarIconContainerView margin usage

Let's put FlexLayout's SetIgnoreDefaultMainAxisMargins through some
real-world usage.

Bug: chromium:943702
Change-Id: I21fb28d21494f9df0045ac9e31ed2fd26875bdc7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1739648
Auto-Submit: Peter Boström <pbos@chromium.org>
Commit-Queue: Dana Fried <dfried@chromium.org>
Reviewed-by: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/master@{#684472}

chrome/browser/ui/views/toolbar/toolbar_icon_container_view.cc

@@ -17,9 +17,10 @@
 ToolbarIconContainerView::ToolbarIconContainerView(bool uses_highlight)
     : uses_highlight_(uses_highlight) {
   auto layout_manager = std::make_unique<views::FlexLayout>();
-  layout_manager->SetCollapseMargins(true).SetDefault(
-      views::kMarginsKey,
-      gfx::Insets(0, 0, 0, GetLayoutConstant(TOOLBAR_ELEMENT_PADDING)));
+  layout_manager->SetCollapseMargins(true)
+      .SetIgnoreDefaultMainAxisMargins(true)
+      .SetDefault(views::kMarginsKey,
+                  gfx::Insets(0, GetLayoutConstant(TOOLBAR_ELEMENT_PADDING)));
   SetLayoutManager(std::move(layout_manager));
 }
 
@@ -29,9 +30,6 @@ void ToolbarIconContainerView::UpdateAllIcons() {}
 
 void ToolbarIconContainerView::AddMainButton(views::Button* main_button) {
   DCHECK(!main_button_);
-  // Set empty margins from this view to remove the default ones set in the
-  // constructor.
-  main_button->SetProperty(views::kMarginsKey, gfx::Insets());
   main_button->AddObserver(this);
   main_button->AddButtonObserver(this);
   main_button_ = main_button;