Update shelf spacing in Chrome OS according to the MD specs

ash/system/tray/system_tray.cc

Index: ash/system/tray/system_tray.cc
diff --git a/ash/system/tray/system_tray.cc b/ash/system/tray/system_tray.cc
index 28b3392d221dc39a3a6726d4c79763869c3c715c..52901e687841c93eec14ed9e84f8af80dd2de045 100644
--- a/ash/system/tray/system_tray.cc
+++ b/ash/system/tray/system_tray.cc
@@ -5,6 +5,7 @@
 #include "ash/system/tray/system_tray.h"
 
 #include "ash/ash_switches.h"
+#include "ash/material_design/material_design_controller.h"
 #include "ash/metrics/user_metrics_recorder.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shelf/shelf_util.h"
@@ -706,6 +707,26 @@ TrayCast* SystemTray::GetTrayCastForTesting() const { return tray_cast_; }
 
 TrayDate* SystemTray::GetTrayDateForTesting() const { return tray_date_; }
 
+void SystemTray::GetHitRegionInsets(gfx::Insets& insets) {
+  if (ash::MaterialDesignController::IsShelfMaterial()) {
+    int top_edge, left_edge, bottom_edge, right_edge;
+    if (wm::IsHorizontalAlignment(shelf_alignment())) {
+      top_edge = (GetShelfLayoutConstant(SHELF_SIZE) - kShelfItemHeight) / 2;
+      left_edge = 0;
+      bottom_edge = (GetShelfLayoutConstant(SHELF_SIZE) - kShelfItemHeight) / 2;
+      right_edge = GetTrayConstant(PADDING_FROM_EDGE_OF_SHELF);
+    } else {  // SHELF_ALIGNMENT_LEFT || SHELF_ALIGNMENT_RIGHT
+      top_edge = 0;
+      left_edge = (GetShelfLayoutConstant(SHELF_SIZE) - kShelfItemHeight) / 2;
+      bottom_edge = GetTrayConstant(PADDING_FROM_EDGE_OF_SHELF);
+      right_edge = (GetShelfLayoutConstant(SHELF_SIZE) - kShelfItemHeight) / 2;
+    }
+    insets.Set(top_edge, left_edge, bottom_edge, right_edge);
+  } else {
+    TrayBackgroundView::GetHitRegionInsets(insets);
+  }
+}
+
 bool SystemTray::PerformAction(const ui::Event& event) {
   // If we're already showing the default view, hide it; otherwise, show it
   // (and hide any popup that's currently shown).