[Picture in Picture] Increase window border thickness.

Increasing the border thickness for a larger surface area to be able
to resize the window. This change is initiated from feedback to have
a larger drag-to-resize area.

This is currently an arbitrary value to gain feedback on the experience.

BUG: 726621
Change-Id: Id02837b86e7851cbe5399a2a1ef9f01905b6fefb
Reviewed-on: https://chromium-review.googlesource.com/1011209Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Commit-Queue: apacible <apacible@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550797}

chrome/browser/ui/views/overlay/overlay_window_views.cc

@@ -24,7 +24,7 @@ std::unique_ptr<content::OverlayWindow> content::OverlayWindow::Create(
 }
 
 namespace {
-const int kBorderThickness = 1;
+const int kBorderThickness = 5;
 const int kResizeAreaCornerSize = 16;
 }  // namespace