Fix tabstrip on Windows with TabScrolling turned on

While the widths of everything were working correctly with the tabstrip, it seems the height was not. This corrects that, and it seems to be a common pattern with other ScrollViews as well.

Bug: 1093529
Change-Id: I31250a62c06c0534c1ab21868df2419313515563
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2252633Reviewed-by: Taylor Bergquist <tbergquist@chromium.org>
Commit-Queue: Connie Wan <connily@chromium.org>
Cr-Commit-Position: refs/heads/master@{#780989}

chrome/browser/ui/views/frame/tab_strip_region_view.cc

@@ -5,6 +5,7 @@
 #include "chrome/browser/ui/views/frame/tab_strip_region_view.h"
 
 #include "base/bind.h"
+#include "chrome/browser/ui/layout_constants.h"
 #include "chrome/browser/ui/ui_features.h"
 #include "ui/views/controls/scroll_view.h"
 #include "ui/views/layout/flex_layout.h"
@@ -32,6 +33,7 @@ TabStrip* TabStripRegionView::AddTabStrip(std::unique_ptr<TabStrip> tab_strip) {
         AddChildView(std::make_unique<views::ScrollView>());
     tab_strip_scroll_container->SetBackgroundColor(base::nullopt);
     tab_strip_scroll_container->SetHideHorizontalScrollBar(true);
+    tab_strip_scroll_container->ClipHeightTo(0, GetLayoutConstant(TAB_HEIGHT));
     tab_strip_container_ = tab_strip_scroll_container;
     return tab_strip_scroll_container->SetContents(std::move(tab_strip));
   } else {