Increase ListMenuButton width

Some of the items in the downloads menu were wrapping because the menu
wasn't wide enough. Increase the width as a short-term fix.

BUG=821949

Change-Id: If4c7445d028354b159d40182d28a263bc59438ec
Reviewed-on: https://chromium-review.googlesource.com/963678Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543420}

chrome/android/java/res/values/dimens.xml

@@ -489,7 +489,7 @@
     <dimen name="list_item_start_icon_width">36dp</dimen>
     <dimen name="list_item_start_icon_corner_radius">18dp</dimen>
     <dimen name="list_item_end_icon_width">56dp</dimen>
-    <dimen name="list_menu_width">140dp</dimen>
+    <dimen name="list_menu_width">180dp</dimen>
 
     <!-- SelectableListLayout dimensions -->
     <dimen name="selectable_list_layout_row_padding">16dp</dimen>