Consolidate FilterOperation and FilterEffect mapRect implementations

third_party/WebKit/Source/platform/graphics/filters/FEGaussianBlur.cpp

Index: third_party/WebKit/Source/platform/graphics/filters/FEGaussianBlur.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/filters/FEGaussianBlur.cpp b/third_party/WebKit/Source/platform/graphics/filters/FEGaussianBlur.cpp
index 1527161d5a95be30a359dca05bd8921534a50ecf..590d839d709eb24459b7d3f2b6e6ea8f7438a474 100644
--- a/third_party/WebKit/Source/platform/graphics/filters/FEGaussianBlur.cpp
+++ b/third_party/WebKit/Source/platform/graphics/filters/FEGaussianBlur.cpp
@@ -31,54 +31,41 @@
 
 #include "SkBlurImageFilter.h"
 
-static inline float gaussianKernelFactor() {
-  return 3 / 4.f * sqrtf(twoPiFloat);
-}
-
 namespace blink {
 
-FEGaussianBlur::FEGaussianBlur(Filter* filter, float x, float y)
-    : FilterEffect(filter), m_stdX(x), m_stdY(y) {}
+namespace {
 
-FEGaussianBlur* FEGaussianBlur::create(Filter* filter, float x, float y) {
-  return new FEGaussianBlur(filter, x, y);
+inline unsigned approximateBoxWidth(float s) {
+  return static_cast<unsigned>(
+      floorf(s * (3 / 4.f * sqrtf(twoPiFloat)) + 0.5f));
 }
 
-IntSize FEGaussianBlur::calculateUnscaledKernelSize(const FloatPoint& std) {
-  ASSERT(std.x() >= 0 && std.y() >= 0);
-
+IntSize calculateKernelSize(const FloatSize& std) {
+  DCHECK(std.width() >= 0 && std.height() >= 0);
   IntSize kernelSize;
-  // Limit the kernel size to 1000. A bigger radius won't make a big difference
-  // for the result image but inflates the absolute paint rect too much. This is
-  // compatible with Firefox' behavior.
-  if (std.x()) {
-    int size = std::max<unsigned>(
-        2,
-        static_cast<unsigned>(floorf(std.x() * gaussianKernelFactor() + 0.5f)));
+  if (std.width()) {
+    int size = std::max<unsigned>(2, approximateBoxWidth(std.width()));
     kernelSize.setWidth(size);
   }
-
-  if (std.y()) {
-    int size = std::max<unsigned>(
-        2,
-        static_cast<unsigned>(floorf(std.y() * gaussianKernelFactor() + 0.5f)));
+  if (std.height()) {
+    int size = std::max<unsigned>(2, approximateBoxWidth(std.height()));
     kernelSize.setHeight(size);
   }
-
   return kernelSize;
 }
 
-IntSize FEGaussianBlur::calculateKernelSize(const Filter* filter,
-                                            const FloatPoint& std) {
-  FloatPoint stdError(filter->applyHorizontalScale(std.x()),
-                      filter->applyVerticalScale(std.y()));
-  return calculateUnscaledKernelSize(stdError);
 }
 
-FloatRect FEGaussianBlur::mapEffect(const FloatRect& rect) const {
-  IntSize kernelSize =
-      calculateKernelSize(getFilter(), FloatPoint(m_stdX, m_stdY));
+FEGaussianBlur::FEGaussianBlur(Filter* filter, float x, float y)
+    : FilterEffect(filter), m_stdX(x), m_stdY(y) {}
 
+FEGaussianBlur* FEGaussianBlur::create(Filter* filter, float x, float y) {
+  return new FEGaussianBlur(filter, x, y);
+}
+
+FloatRect FEGaussianBlur::mapEffect(const FloatSize& stdDeviation,
+                                    const FloatRect& rect) {
+  IntSize kernelSize = calculateKernelSize(stdDeviation);
   // We take the half kernel size and multiply it by three, because we run box
   // blur three times.
   FloatRect result = rect;
@@ -87,6 +74,12 @@ FloatRect FEGaussianBlur::mapEffect(const FloatRect& rect) const {
   return result;
 }
 
+FloatRect FEGaussianBlur::mapEffect(const FloatRect& rect) const {
+  FloatSize stdError(getFilter()->applyHorizontalScale(m_stdX),
+                     getFilter()->applyVerticalScale(m_stdY));
+  return mapEffect(stdError, rect);
+}
+
 sk_sp<SkImageFilter> FEGaussianBlur::createImageFilter() {
   sk_sp<SkImageFilter> input(
       SkiaImageFilterBuilder::build(inputEffect(0), operatingColorSpace()));