MacViews: Overlay Scrollbars with Show/Hide Animations

ui/native_theme/native_theme.h

Index: ui/native_theme/native_theme.h
diff --git a/ui/native_theme/native_theme.h b/ui/native_theme/native_theme.h
index b09dd15b1c17171fe6dffbb7aa1f9b100bd4e920..6980eb863296f9feb060f5ed2d3368b8fdba837e 100644
--- a/ui/native_theme/native_theme.h
+++ b/ui/native_theme/native_theme.h
@@ -97,6 +97,14 @@ class NATIVE_THEME_EXPORT NativeTheme {
     kNumStates = kPressed + 1,
   };
 
+  // Struct that holds overlay information.
+  // If is_overlay is set to false, then the part is not overlay-styled
+  // and the alpha value should be ignored.
+  struct OverlayParams {
+    double alpha;
+    double is_overlay;

[tapted, 2016/02/08 00:31:15]

double -> bool?

[spqchan, 2016/02/09 21:21:25]

Whoops, done

+  };
+
   // Each structure below holds extra information needed when painting a given
   // part.
 
@@ -160,6 +168,7 @@ class NATIVE_THEME_EXPORT NativeTheme {
 
   struct ScrollbarArrowExtraParams {
     bool is_hovering;
+    OverlayParams overlay;
   };
 
   struct ScrollbarTrackExtraParams {
@@ -168,11 +177,13 @@ class NATIVE_THEME_EXPORT NativeTheme {
     int track_y;
     int track_width;
     int track_height;
+    OverlayParams overlay;
     int classic_state;  // Used on Windows when uxtheme is not available.
   };
 
   struct ScrollbarThumbExtraParams {
     bool is_hovering;
+    OverlayParams overlay;
   };
 
   struct SliderExtraParams {