[ash-md] Disables rounded corners by default in overview mode

ash/common/wm/overview/window_grid.cc

Index: ash/common/wm/overview/window_grid.cc
diff --git a/ash/common/wm/overview/window_grid.cc b/ash/common/wm/overview/window_grid.cc
index 114dddf4dc56bf0ffd05b691b483506b18f8622c..f1a5b4637f07ab05b0b47e919aff74988b1d9084 100644
--- a/ash/common/wm/overview/window_grid.cc
+++ b/ash/common/wm/overview/window_grid.cc
@@ -74,7 +74,9 @@ const int kMinCardsMajor = 3;
 
 // Hiding window headers can be resource intensive. Only hide the headers when
 // the number of windows in this grid is less or equal than this number.
-const int kMaxWindowsCountToHideHeader = 10;
+// The default is 0, meaning that mask layers are never used and the bottom
+// corners are not rounded in overview.
+const int kMaxWindowsCountToHideHeaderWithMasks = 0;
 
 const int kOverviewSelectorTransitionMilliseconds = 250;
 
@@ -460,13 +462,13 @@ void WindowGrid::PositionWindowsMD(bool animate) {
   const size_t windows_count = window_list_.size();
   const base::CommandLine* command_line =
       base::CommandLine::ForCurrentProcess();
-  int windows_to_use_masks = kMaxWindowsCountToHideHeader;
+  int windows_to_use_masks = kMaxWindowsCountToHideHeaderWithMasks;
   if (command_line->HasSwitch(switches::kAshMaxWindowsToUseMaskInOverview) &&
       (!base::StringToInt(command_line->GetSwitchValueASCII(
                               switches::kAshMaxWindowsToUseMaskInOverview),
                           &windows_to_use_masks) ||
        windows_to_use_masks <= kUnlimited)) {
-    windows_to_use_masks = kMaxWindowsCountToHideHeader;
+    windows_to_use_masks = kMaxWindowsCountToHideHeaderWithMasks;
   }
   int windows_to_use_shapes = kUnlimited;
   if (command_line->HasSwitch(switches::kAshMaxWindowsToUseShapeInOverview) &&