forward declare missing colors

atom/browser/api/atom_api_system_preferences_mac.mm

@@ -7,13 +7,13 @@
 #include <map>
 
 #import <AVFoundation/AVFoundation.h>
-#import <AppKit/NSColor.h>
 #import <Cocoa/Cocoa.h>
 
 #include "atom/browser/mac/atom_application.h"
 #include "atom/browser/mac/dict_util.h"
 #include "atom/common/native_mate_converters/gurl_converter.h"
 #include "atom/common/native_mate_converters/value_converter.h"
+#include "base/strings/stringprintf.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/values.h"
 #include "native_mate/object_template_builder.h"
@@ -107,12 +107,9 @@ AVMediaType ParseMediaType(const std::string& media_type) {
 
 // Convert color to RGB hex value like "#ABCDEF"
 std::string ToRGBHex(NSColor* color) {
-  NSString* rgbHex = [NSString
-      stringWithFormat:@"#%02X%02X%02X", (int)(color.redComponent * 0xFF),
-                       (int)(color.greenComponent * 0xFF),
-                       (int)(color.blueComponent * 0xFF)];
-
-  return std::string([rgbHex UTF8String]);
+  return base::StringPrintf("#%02X%02X%02X", (int)(color.redComponent * 0xFF),
+                            (int)(color.greenComponent * 0xFF),
+                            (int)(color.blueComponent * 0xFF));
 }
 
 }  // namespace

atom/browser/mac/atom_application.h

@@ -37,6 +37,27 @@ typedef NS_ENUM(NSInteger, AVAuthorizationStatusMac) {
     (AVMediaType)mediaType API_AVAILABLE(macosx(10.14));
 @end
 
+@interface NSColor (MojaveSDK)
+@property(class, strong, readonly)
+    NSColor* systemBlueColor API_AVAILABLE(macosx(10.10));
+@property(class, strong, readonly)
+    NSColor* systemBrownColor API_AVAILABLE(macosx(10.10));
+@property(class, strong, readonly)
+    NSColor* systemGrayColor API_AVAILABLE(macosx(10.10));
+@property(class, strong, readonly)
+    NSColor* systemGreenColor API_AVAILABLE(macosx(10.10));
+@property(class, strong, readonly)
+    NSColor* systemOrangeColor API_AVAILABLE(macosx(10.10));
+@property(class, strong, readonly)
+    NSColor* systemPinkColor API_AVAILABLE(macosx(10.10));
+@property(class, strong, readonly)
+    NSColor* systemPurpleColor API_AVAILABLE(macosx(10.10));
+@property(class, strong, readonly)
+    NSColor* systemRedColor API_AVAILABLE(macosx(10.10));
+@property(class, strong, readonly)
+    NSColor* systemYellowColor API_AVAILABLE(macosx(10.10));
+@end
+
 extern "C" {
 #if !defined(MAC_OS_X_VERSION_10_14) || \
     MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_14