Add shadow for md toggle button.

ui/views/controls/button/toggle_button.cc

Index: ui/views/controls/button/toggle_button.cc
diff --git a/ui/views/controls/button/toggle_button.cc b/ui/views/controls/button/toggle_button.cc
index 9d700a8b4e77e5830d948640bbb6622f43ae1c89..4a4cb3d7c1006f427aea8bb5b14623ebeb62bd8f 100644
--- a/ui/views/controls/button/toggle_button.cc
+++ b/ui/views/controls/button/toggle_button.cc
@@ -4,6 +4,8 @@
 
 #include "ui/views/controls/button/toggle_button.h"
 
+#include "third_party/skia/include/core/SkDrawLooper.h"
+#include "third_party/skia/include/core/SkPaint.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/views/border.h"
@@ -16,10 +18,13 @@ namespace {
 const int kTrackHeight = 14;
 const int kTrackWidth = 36;
 // Margins from edge of track to edge of view.
-const int kTrackVerticalMargin = 4;
-const int kTrackHorizontalMargin = 1;
-// Margin from edge of thumb to closest three edges of view.
-const int kThumbMargin = 1;
+const int kTrackVerticalMargin = 6;
+const int kTrackHorizontalMargin = 2;
+// Margin from edge of thumb to closest edge of view. Note that the thumb
+// margins must be sufficiently large to allow space for the shadow.
+const int kThumbHorizontalMargin = 2;
+// Margin from top/bottom edge of thumb to top/bottom edge of view.
+const int kThumbVerticalMargin = 3;
 
 }  // namespace
 
@@ -57,38 +62,43 @@ void ToggleButton::OnPaint(gfx::Canvas* canvas) {
   SkAlpha blend =
       static_cast<SkAlpha>(SK_AlphaOPAQUE * slide_animation_.GetCurrentValue());
 
-  gfx::RectF track_rect(GetContentsBounds());
-  SkPaint paint;
-  paint.setAntiAlias(true);
-
   // Track.
+  gfx::RectF track_rect(GetContentsBounds());
+  SkPaint track_paint;
+  track_paint.setAntiAlias(true);
   const SkColor track_on_color =
       SkColorSetA(GetNativeTheme()->GetSystemColor(
                       ui::NativeTheme::kColorId_CallToActionColor),
                   0xFF / 2);
   // TODO(estade): get this color from the theme.
   const SkColor track_off_color = SkColorSetA(SK_ColorBLACK, 0x61);
-  paint.setColor(
+  track_paint.setColor(
       color_utils::AlphaBlend(track_on_color, track_off_color, blend));
-  canvas->DrawRoundRect(track_rect, track_rect.height() / 2, paint);
+  canvas->DrawRoundRect(track_rect, track_rect.height() / 2, track_paint);
 
   // Thumb.
-  const SkColor thumb_on_color = GetNativeTheme()->GetSystemColor(
-      ui::NativeTheme::kColorId_CallToActionColor);
-  // TODO(estade): get this color from the theme.
-  const SkColor thumb_off_color = SkColorSetRGB(0xFA, 0xFA, 0xFA);
-  paint.setColor(
-      color_utils::AlphaBlend(thumb_on_color, thumb_off_color, blend));
   gfx::Rect thumb_bounds = GetLocalBounds();
-  thumb_bounds.Inset(gfx::Insets(kThumbMargin));
+  thumb_bounds.Inset(gfx::Insets(kThumbVerticalMargin, kThumbHorizontalMargin));
   thumb_bounds.set_x(thumb_bounds.x() +
                      slide_animation_.GetCurrentValue() *
                          (thumb_bounds.width() - thumb_bounds.height()));
   thumb_bounds.set_width(thumb_bounds.height());
   thumb_bounds.set_x(GetMirroredXForRect(thumb_bounds));
+  SkPaint thumb_paint;
+  std::vector<gfx::ShadowValue> shadows;
+  shadows.emplace_back(gfx::Vector2d(0, 1), 5.f,
+                       SkColorSetA(SK_ColorBLACK, 0x99));
+  thumb_paint.setLooper(gfx::CreateShadowDrawLooperCorrectBlur(shadows));
+  thumb_paint.setStyle(SkPaint::kStrokeAndFill_Style);
+  thumb_paint.setAntiAlias(true);
+  const SkColor thumb_on_color = GetNativeTheme()->GetSystemColor(
+      ui::NativeTheme::kColorId_CallToActionColor);
+  // TODO(estade): get this color from the theme.
+  const SkColor thumb_off_color = SkColorSetRGB(0xFA, 0xFA, 0xFA);
+  thumb_paint.setColor(
+      color_utils::AlphaBlend(thumb_on_color, thumb_off_color, blend));
   canvas->DrawCircle(gfx::RectF(thumb_bounds).CenterPoint(),
-                     thumb_bounds.height() / 2.f, paint);
-  // TODO(estade): add a shadow to the thumb.
+                     thumb_bounds.height() / 2.f, thumb_paint);
 }
 
 void ToggleButton::NotifyClick(const ui::Event& event) {