Adjust sizes of material design shadows based on Sebastien's feedback.

ui/gfx/skia_util.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/skia_util.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/numerics/safe_conversions.h"
@@ skipping 114 matching lines @@
                                             SkColor end_color) {
   SkColor grad_colors[2] = { start_color, end_color};
   SkPoint grad_points[2];
   grad_points[0].iset(0, start_point);
   grad_points[1].iset(0, end_point);
 
   return SkGradientShader::MakeLinear(
       grad_points, grad_colors, NULL, 2, SkShader::kClamp_TileMode);
 }
 
-static SkScalar RadiusToSigma(double radius) {
+// TODO(estade): remove. Only exists to support legacy CreateShadowDrawLooper.
+static SkScalar DeprecatedRadiusToSigma(double radius) {
   // This captures historically what skia did under the hood. Now skia accepts
   // sigma, not radius, so we perform the conversion.
   return radius > 0 ? SkDoubleToScalar(0.57735f * radius + 0.5) : 0;
 }
 
+// This is copied from
+// third_party/WebKit/Source/platform/graphics/skia/SkiaUtils.h
+static SkScalar RadiusToSigma(double radius) {
+  return radius > 0 ? SkDoubleToScalar(0.288675f * radius + 0.5f) : 0;
+}
+
 sk_sp<SkDrawLooper> CreateShadowDrawLooper(
     const std::vector<ShadowValue>& shadows) {
   if (shadows.empty())
     return nullptr;
 
   SkLayerDrawLooper::Builder looper_builder;
 
   looper_builder.addLayer();  // top layer of the original.
 
   SkLayerDrawLooper::LayerInfo layer_info;
   layer_info.fPaintBits |= SkLayerDrawLooper::kMaskFilter_Bit;
   layer_info.fPaintBits |= SkLayerDrawLooper::kColorFilter_Bit;
   layer_info.fColorMode = SkXfermode::kSrc_Mode;
 
   for (size_t i = 0; i < shadows.size(); ++i) {
     const ShadowValue& shadow = shadows[i];
 
     layer_info.fOffset.set(SkIntToScalar(shadow.x()),
                            SkIntToScalar(shadow.y()));
 
     SkPaint* paint = looper_builder.addLayer(layer_info);
     // SkBlurMaskFilter's blur radius defines the range to extend the blur from
     // original mask, which is half of blur amount as defined in ShadowValue.
+    // Note that because this function uses DeprecatedRadiusToSigma, it actually
+    // creates a draw looper with roughly twice the desired blur.
+    paint->setMaskFilter(SkBlurMaskFilter::Make(
+        kNormal_SkBlurStyle, DeprecatedRadiusToSigma(shadow.blur() / 2),
+        SkBlurMaskFilter::kHighQuality_BlurFlag));
+    paint->setColorFilter(
+        SkColorFilter::MakeModeFilter(shadow.color(),
+                                      SkXfermode::kSrcIn_Mode));
+  }
+
+  return looper_builder.detach();
+}
+
+sk_sp<SkDrawLooper> CreateShadowDrawLooperCorrectBlur(
+    const std::vector<ShadowValue>& shadows) {
+  if (shadows.empty())
+    return nullptr;
+
+  SkLayerDrawLooper::Builder looper_builder;
+
+  looper_builder.addLayer();  // top layer of the original.
+
+  SkLayerDrawLooper::LayerInfo layer_info;
+  layer_info.fPaintBits |= SkLayerDrawLooper::kMaskFilter_Bit;
+  layer_info.fPaintBits |= SkLayerDrawLooper::kColorFilter_Bit;
+  layer_info.fColorMode = SkXfermode::kSrc_Mode;
+
+  for (size_t i = 0; i < shadows.size(); ++i) {
+    const ShadowValue& shadow = shadows[i];
+
+    layer_info.fOffset.set(SkIntToScalar(shadow.x()),
+                           SkIntToScalar(shadow.y()));
+
+    SkPaint* paint = looper_builder.addLayer(layer_info);
+    // SkBlurMaskFilter's blur radius defines the range to extend the blur from
+    // original mask, which is half of blur amount as defined in ShadowValue.
     paint->setMaskFilter(SkBlurMaskFilter::Make(
         kNormal_SkBlurStyle, RadiusToSigma(shadow.blur() / 2),
         SkBlurMaskFilter::kHighQuality_BlurFlag));
     paint->setColorFilter(
         SkColorFilter::MakeModeFilter(shadow.color(),
                                       SkXfermode::kSrcIn_Mode));
   }
 
   return looper_builder.detach();
 }
@@ skipping 59 matching lines @@
   static const SkScalar kSkToHbRatio = SK_Scalar1 / kHbUnit1;
   return kSkToHbRatio * value;
 }
 
 float HarfBuzzUnitsToFloat(int value) {
   static const float kFloatToHbRatio = 1.0f / kHbUnit1;
   return kFloatToHbRatio * value;
 }
 
 }  // namespace gfx