Only support left/right maximizing at 50% width when the --ash-enable-alternate-caption-button

ash/ash_switches.h

Index: ash/ash_switches.h
diff --git a/ash/ash_switches.h b/ash/ash_switches.h
index bbf026a32cde4776070b578ed211f67548fb6e6b..6470be434df7709bf14475a5d5c3b9fde8713278 100644
--- a/ash/ash_switches.h
+++ b/ash/ash_switches.h
@@ -30,6 +30,7 @@ ASH_EXPORT extern const char kAshDisableAlternateShelfLayout[];
 #if defined(OS_CHROMEOS)
 ASH_EXPORT extern const char kAshDisableAudioDeviceMenu[];
 #endif
+ASH_EXPORT extern const char kAshDisableAlternateFrameCaptionButtonStyle[];
 ASH_EXPORT extern const char kAshDisableAutoMaximizing[];
 ASH_EXPORT extern const char kAshDisableDisplayChangeLimiter[];
 ASH_EXPORT extern const char kAshDisableDragOffShelf[];
@@ -43,6 +44,7 @@ ASH_EXPORT extern const char kAshDisableUsbChargerNotification[];
 ASH_EXPORT extern const char kAshEnableAudioDeviceMenu[];
 #endif
 ASH_EXPORT extern const char kAshEnableAdvancedGestures[];
+ASH_EXPORT extern const char kAshEnableAlternateFrameCaptionButtonStyle[];
 ASH_EXPORT extern const char kAshEnableBrightnessControl[];
 ASH_EXPORT extern const char kAshEnableDockedWindows[];
 #if defined(OS_LINUX)
@@ -69,6 +71,10 @@ ASH_EXPORT extern const char kForcedMaximizeMode[];
 ASH_EXPORT extern const char kShowShelfAlignmentMenu[];
 ASH_EXPORT extern const char kHideShelfAlignmentMenu[];
 
+// Returns true if the alternate visual style for the caption buttons (minimize,
+// maximize, restore, close) should be used.
+ASH_EXPORT bool UseAlternateFrameCaptionButtonStyle();
+
 // Returns true if the alternate shelf layout should be used.
 ASH_EXPORT bool UseAlternateShelfLayout();