Change print setting conventions for margins to support more options.

printing/print_job_constants.h

Index: printing/print_job_constants.h
diff --git a/printing/print_job_constants.h b/printing/print_job_constants.h
index cbdad74fb85283a4a643665d0725cf6468c76d0f..4fa60a36e01ec82952554fcbaa48a9f29206e3dc 100644
--- a/printing/print_job_constants.h
+++ b/printing/print_job_constants.h
@@ -19,7 +19,6 @@ PRINTING_EXPORT extern const char kSettingColor[];
 PRINTING_EXPORT extern const char kSettingContentHeight[];
 PRINTING_EXPORT extern const char kSettingContentWidth[];
 PRINTING_EXPORT extern const char kSettingCopies[];
-PRINTING_EXPORT extern const char kSettingDefaultMarginsSelected[];
 PRINTING_EXPORT extern const char kSettingDeviceName[];
 PRINTING_EXPORT extern const char kSettingDuplexMode[];
 PRINTING_EXPORT extern const char kSettingGenerateDraftData[];
@@ -38,7 +37,12 @@ PRINTING_EXPORT extern const char kSettingMarginBottom[];
 PRINTING_EXPORT extern const char kSettingMarginLeft[];
 PRINTING_EXPORT extern const char kSettingMarginRight[];
 PRINTING_EXPORT extern const char kSettingMarginTop[];
-PRINTING_EXPORT extern const char kSettingMargins[];
+PRINTING_EXPORT extern const char kSettingMarginsCustom[];
+PRINTING_EXPORT extern const char kSettingMarginsType[];
+PRINTING_EXPORT extern const char kSettingMarginsTypeCustom[];
+PRINTING_EXPORT extern const char kSettingMarginsTypeDefault[];
+PRINTING_EXPORT extern const char kSettingMarginsTypeNone[];
+PRINTING_EXPORT extern const char kSettingMarginsTypePrintableArea[];
 PRINTING_EXPORT extern const char kSettingPageRange[];
 PRINTING_EXPORT extern const char kSettingPageRangeFrom[];
 PRINTING_EXPORT extern const char kSettingPageRangeTo[];