[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 9652e5deefc6fb2d85b274d0a482d19c0639dedc..4b9ab46c72c731450641f9fe8b3a80bdc51b2c02 100644
--- a/ash/common/wm/overview/window_grid.cc
+++ b/ash/common/wm/overview/window_grid.cc
@@ -76,7 +76,9 @@ 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;
 
@@ -462,13 +464,13 @@ 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) &&