Overlay scrollbars flush with window edge

ui/native_theme/native_theme_aura.cc

Index: ui/native_theme/native_theme_aura.cc
diff --git a/ui/native_theme/native_theme_aura.cc b/ui/native_theme/native_theme_aura.cc
index 76283878e06a13f8cb77b8adbc90799dfea2aa28..39d85793599d7a1b97bb374623fba3878857f293 100644
--- a/ui/native_theme/native_theme_aura.cc
+++ b/ui/native_theme/native_theme_aura.cc
@@ -186,7 +186,7 @@ void NativeThemeAura::PaintScrollbarThumb(
     Part part,
     State state,
     const gfx::Rect& rect,
-    ScrollbarOverlayColorTheme theme) const {
+    const NativeTheme::ScrollbarThumbExtraParams& params) const {
   // Do not paint if state is disabled.
   if (state == kDisabled)
     return;
@@ -212,7 +212,7 @@ void NativeThemeAura::PaintScrollbarThumb(
     constexpr SkColor kOverlayScrollbarStrokeColor[] = {SK_ColorWHITE,
                                                         SK_ColorBLACK};
 
-    thumb_color = kOverlayScrollbarThumbColor[theme];
+    thumb_color = kOverlayScrollbarThumbColor[params.scrollbar_theme];
 
     SkAlpha stroke_alpha = SK_AlphaTRANSPARENT;
     switch (state) {
@@ -237,6 +237,7 @@ void NativeThemeAura::PaintScrollbarThumb(
         break;
     }
 
+#if defined(OS_ANDROID)

[bokan, 2017/03/22 20:07:25]

This file is only compiled for Aura platforms so Chrome OS, Linux, Windows. You
shouldn't need an ifdef here.

     // In overlay mode, draw a stroke (border).
     constexpr int kStrokeWidth = kOverlayScrollbarStrokeWidth;
     cc::PaintFlags flags;
@@ -252,6 +253,56 @@ void NativeThemeAura::PaintScrollbarThumb(
 
     // Inset the all the edges edges so we fill-in the stroke below.
     thumb_rect.Inset(kStrokeWidth, kStrokeWidth);
+#else  // OS_ANDROID
+    // In overlay mode, draw a stroke (border).
+    constexpr int kStrokeWidth = kOverlayScrollbarStrokeWidth;
+    cc::PaintFlags flags;
+    flags.setColor(SkColorSetA(
+        kOverlayScrollbarStrokeColor[params.scrollbar_theme], stroke_alpha));
+    flags.setStyle(cc::PaintFlags::kStroke_Style);
+    flags.setStrokeWidth(kStrokeWidth);
+
+    gfx::RectF stroke_rect(thumb_rect);
+    constexpr float kHalfStrokeWidth = kStrokeWidth / 2.f;
+
+    float left_stroke_width, top_stroke_width, right_stroke_width,
+        bottom_stroke_width;
+
+    left_stroke_width = top_stroke_width = right_stroke_width =
+        bottom_stroke_width = kHalfStrokeWidth;
+
+    if (params.isLeftVerticalScrollbar) {
+      left_stroke_width = 0;
+    } else if (params.isVerticalScrollbar) {
+      right_stroke_width = 0;
+    } else {
+      bottom_stroke_width = 0;
+    }
+
+    if (params.hitStart) {
+      if (params.isVerticalScrollbar) {
+        top_stroke_width = 0;
+      } else {
+        left_stroke_width = 0;
+      }
+    }
+
+    if (params.hitEnd) {
+      if (params.isVerticalScrollbar) {
+        bottom_stroke_width = 0;
+      } else {
+        right_stroke_width = 0;
+      }
+    }
+
+    stroke_rect.Inset(left_stroke_width, top_stroke_width, right_stroke_width,
+                      bottom_stroke_width);
+    canvas->drawRect(gfx::RectFToSkRect(stroke_rect), flags);
+
+    // Inset the all the edges edges so we fill-in the stroke below.
+    thumb_rect.Inset(left_stroke_width * 2, top_stroke_width * 2,
+                     right_stroke_width * 2, bottom_stroke_width * 2);
+#endif
   } else {
     switch (state) {
       case NativeTheme::kDisabled: