Add context to gfx::Screen calls in support of simultaneous desktop+ash

ash/tooltips/tooltip_controller.cc

Index: ash/tooltips/tooltip_controller.cc
diff --git a/ash/tooltips/tooltip_controller.cc b/ash/tooltips/tooltip_controller.cc
index fd70c0df193d8fe0687bb859c5727d0ff9c37752..0cd5e423a5666050e599b6edaaa23934d7a95747 100644
--- a/ash/tooltips/tooltip_controller.cc
+++ b/ash/tooltips/tooltip_controller.cc
@@ -69,7 +69,9 @@ int GetMaxWidth(int x, int y) {
   // TODO(varunjain): implementation duplicated in tooltip_manager_aura. Figure
   // out a way to merge.
   gfx::Rect display_bounds =
-      gfx::Screen::GetDisplayNearestPoint(gfx::Point(x, y)).bounds();
+      gfx::Screen::GetDisplayNearestPoint(
+          ash::Shell::GetPrimaryRootWindow(),
+          gfx::Point(x, y)).bounds();
   return (display_bounds.width() + 1) / 2;
 }
 
@@ -165,7 +167,9 @@ class TooltipController::Tooltip : public views::WidgetObserver {
 
     tooltip_rect.Offset(kCursorOffsetX, kCursorOffsetY);
     gfx::Rect display_bounds =
-        gfx::Screen::GetDisplayNearestPoint(tooltip_rect.origin()).bounds();
+        gfx::Screen::GetDisplayNearestPoint(
+            ash::Shell::GetPrimaryRootWindow(),
+            tooltip_rect.origin()).bounds();
 
     // If tooltip is out of bounds on the x axis, we simply shift it
     // horizontally by the offset.