Align the base of the shelf's context menu to the top edge of the shelf.

ui/views/controls/menu/menu_controller.cc

Index: ui/views/controls/menu/menu_controller.cc
diff --git a/ui/views/controls/menu/menu_controller.cc b/ui/views/controls/menu/menu_controller.cc
index f9aac0a605a8bc1c51c65f28c3bce22e55c81e27..4c1ed3a29a6eceeeb123dd09348b5c7717cdd453 100644
--- a/ui/views/controls/menu/menu_controller.cc
+++ b/ui/views/controls/menu/menu_controller.cc
@@ -73,10 +73,6 @@ const int kScrollTimerMS = 30;
 // Amount of time from when the drop exits the menu and the menu is hidden.
 const int kCloseOnExitTime = 1200;
 
-// If a context menu is invoked by touch, we shift the menu by this offset so
-// that the finger does not obscure the menu.
-const int kCenteredContextMenuYOffset = -15;

[minch1, 2017/05/04 16:44:15]

Sorry, not quite sure about here. This is not needed by the shelf context menu
now. But |MENU_ANCHOR_BOTTOMCENTER| is also used by |ToolkitDelegateViews|. I am
not sure whether it is ok to remove this variable here directly? msw@, what's
your opinion?

[msw, 2017/05/05 17:34:19]

This seems wrong, it'll change the positioning of all touch menus, not just the
shelf ones. Perhaps we should be using MENU_ANCHOR_BUBBLE_* for shelf menus?
(ShelfView::ShowMenu is already the only user of those MENU_ANCHOR_BUBBLE_*
values). Or, perhaps (1) add yet another anchor that works like BOTTOMCENTER but
doesn't apply the offset, or (2) make the shelf apply the inverse of this offset
when constructing the menu...

-
 // The spacing offset for the bubble tip.
 const int kBubbleTipSizeLeftRight = 12;
 const int kBubbleTipSizeTopBottom = 11;
@@ -1951,14 +1947,12 @@ gfx::Rect MenuController::CalculateMenuBounds(MenuItemView* item,
         x -= 1;
     } else if (state_.anchor == MENU_ANCHOR_BOTTOMCENTER) {
       x = x - (pref.width() - state_.initial_bounds.width()) / 2;
-      if (pref.height() >
-          state_.initial_bounds.y() + kCenteredContextMenuYOffset) {
-        // Menu does not fit above the anchor. We move it to below.
-        y = state_.initial_bounds.y() - kCenteredContextMenuYOffset;
-      } else {
-        y = std::max(0, state_.initial_bounds.y() - pref.height()) +
-            kCenteredContextMenuYOffset;
-      }
+      // If menu does not fit above the anchor. We move it to below.

[msw, 2017/05/05 17:34:19]

nit: "Place the menu below the anchor if it does not fit above."

+      y = pref.height() > state_.initial_bounds.y()
+              ? state_.initial_bounds.y()
+              : (state_.initial_bounds.y() - pref.height());
+    } else if (state_.anchor == MENU_ANCHOR_SIDECENTER) {
+      y = y - (pref.height() - state_.initial_bounds.height()) / 2;

[msw, 2017/05/05 17:34:19]

nit: y -= (or += with subtraction reversed might be a little simpler?)

     }
 
     if (!state_.monitor_bounds.IsEmpty() &&