Update voice interaction icon shadow

ui/gfx/shadow_value.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gfx/shadow_value.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 62 matching lines @@
 Insets ShadowValue::GetMargin(const ShadowValues& shadows) {
   gfx::Insets margins = GetInsets(shadows, false);
   return -margins;
 }
 
 // static
 Insets ShadowValue::GetBlurRegion(const ShadowValues& shadows) {
   return GetInsets(shadows, true);
 }
 
+// static
+ShadowValues ShadowValue::MakeMdShadowValues(int elevation) {
+  ShadowValues shadow_values;
+  // To match the CSS notion of blur (spread outside the bounding box) to the
+  // Skia notion of blur (spread outside and inside the bounding box), we have
+  // to double the designer-provided blur values.
+  const int kBlurCorrection = 2;
+  // "Key shadow": y offset is elevation and blur is twice the elevation.
+  shadow_values.emplace_back(gfx::Vector2d(0, elevation),
+                             kBlurCorrection * elevation * 2,
+                             SkColorSetA(SK_ColorBLACK, 0x3d));
+  // "Ambient shadow": no offset and blur matches the elevation.
+  shadow_values.emplace_back(gfx::Vector2d(), kBlurCorrection * elevation,
+                             SkColorSetA(SK_ColorBLACK, 0x1f));
+  // To see what this looks like for elevation 24, try this CSS:
+  //   box-shadow: 0 24px 48px rgba(0, 0, 0, .24),
+  //               0 0 24px rgba(0, 0, 0, .12);
+  return shadow_values;
+}
+
 }  // namespace gfx