Fix math error in Mohnstrudel shade opening code.

Without abs(), a drag-left (e.g. to reorder extensions) will be
interpreted as trying to open the tabstrip tray in touch mode.

Bug: 1117274
Change-Id: I535eeb8284bcc9d9406721efbcd9363b820c9d99
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2360596Reviewed-by: Collin Baker <collinbaker@chromium.org>
Commit-Queue: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798916}

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

@@ -274,7 +274,7 @@ class WebUITabStripContainerView::DragToOpenHandler : public ui::EventHandler {
         // scrolls are used in the toolbar, e.g. for text scrolling in
         // the Omnibox.
         if (event->details().scroll_y_hint() >
-            event->details().scroll_x_hint()) {
+            std::fabs(event->details().scroll_x_hint())) {
           drag_in_progress_ = true;
           container_->UpdateHeightForDragToOpen(
               event->details().scroll_y_hint());