servo: Merge #14769 - Update helper functions of StyleComplexColor (from upsuper:complex-color-update); r=heycam

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The definition of `StyleComplexColor` in the Gecko side was updated in [bug 1063162](https://bugzilla.mozilla.org/show_bug.cgi?id=1063162). The helper functions need update as well.

r? @Manishearth

Source-Repo: https://github.com/servo/servo
Source-Revision: bbe70c7c5f07a67c48523221cb5d9ba12cbb2151

servo/components/style/gecko_bindings/structs_debug.rs

@@ -3042,6 +3042,7 @@ pub mod root {
         pub struct StyleComplexColor {
             pub mColor: root::nscolor,
             pub mForegroundRatio: u8,
+            pub mIsAuto: bool,
         }
         #[test]
         fn bindgen_test_layout_StyleComplexColor() {

servo/components/style/gecko_bindings/structs_release.rs

@@ -3024,6 +3024,7 @@ pub mod root {
         pub struct StyleComplexColor {
             pub mColor: root::nscolor,
             pub mForegroundRatio: u8,
+            pub mIsAuto: bool,
         }
         #[test]
         fn bindgen_test_layout_StyleComplexColor() {

servo/components/style/gecko_bindings/sugar/style_complex_color.rs

@@ -11,6 +11,7 @@ impl From<nscolor> for StyleComplexColor {
         StyleComplexColor {
             mColor: other,
             mForegroundRatio: 0,
+            mIsAuto: false,
         }
     }
 }
@@ -20,6 +21,15 @@ impl StyleComplexColor {
         StyleComplexColor {
             mColor: 0,
             mForegroundRatio: 255,
+            mIsAuto: false,
+        }
+    }
+
+    pub fn auto() -> Self {
+        StyleComplexColor {
+            mColor: 0,
+            mForegroundRatio: 255,
+            mIsAuto: true,
         }
     }
 }