[Tab Scrolling] Fix the tabstrip on Windows.

The height of the TabStrip was being incorrectly set when Tab Scrolling
was turned on leading to an invisible tabstrip.

height() is 0, potentially because TabStrip does it's own layout?

Bug: 1093529
Change-Id: I45745b8d3ff0cdbcaf1b5ba99e2e16bc2c23c69d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2364698Reviewed-by: Taylor Bergquist <tbergquist@chromium.org>
Commit-Queue: Charlene Yan <cyan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#799825}

chrome/browser/ui/views/tabs/tab_strip.cc

@@ -2173,7 +2173,7 @@ void TabStrip::Layout() {
     const int available_width = available_width_callback_.Run();
     // It should be as wide as possible subject to the above constraints.
     const int width = std::min(max_width, std::max(min_width, available_width));
-    SetBounds(0, 0, width, height());
+    SetBounds(0, 0, width, GetLayoutConstant(TAB_HEIGHT));
     SetTabSlotVisibility();
   }