Remove SkLerpXfermode

This relies on the Chromium CL https://codereview.chromium.org/1610573004/ (Replace use of SkLerpXfermode with SkArithmeticMode)

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1611633002

Review URL: https://codereview.chromium.org/1611633002

3 files changed, 10 insertions, 130 deletions

diff --git a/src/effects/SkArithmeticMode.cpp b/src/effects/SkArithmeticMode.cpp
index 9eb7dd2198..33783a52f8 100644
--- a/src/effects/SkArithmeticMode.cpp
+++ b/src/effects/SkArithmeticMode.cpp
@@ -21,8 +21,16 @@ static const bool gUseUnpremul = false;
 
 class SkArithmeticMode_scalar : public SkXfermode {
 public:
-    static SkArithmeticMode_scalar* Create(SkScalar k1, SkScalar k2, SkScalar k3, SkScalar k4,
-                                           bool enforcePMColor) {
+    static SkXfermode* Create(SkScalar k1, SkScalar k2, SkScalar k3, SkScalar k4,
+                              bool enforcePMColor) {
+        if (SkScalarNearlyZero(k1) && SkScalarNearlyEqual(k2, SK_Scalar1) &&
+            SkScalarNearlyZero(k3) && SkScalarNearlyZero(k4)) {
+            return SkXfermode::Create(SkXfermode::kSrc_Mode);
+        } else if (SkScalarNearlyZero(k1) && SkScalarNearlyZero(k2) && 
+                   SkScalarNearlyEqual(k3, SK_Scalar1) && SkScalarNearlyZero(k4)) {
+            return SkXfermode::Create(SkXfermode::kDst_Mode);
+        }
+
         return new SkArithmeticMode_scalar(k1, k2, k3, k4, enforcePMColor);
     }
 
diff --git a/src/effects/SkLerpXfermode.cpp b/src/effects/SkLerpXfermode.cpp
deleted file mode 100644
index a069e8b367..0000000000
--- a/src/effects/SkLerpXfermode.cpp
+++ /dev/null
@@ -1,118 +0,0 @@
-/*
- * Copyright 2013 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#include "SkLerpXfermode.h"
-#include "SkColorPriv.h"
-#include "SkReadBuffer.h"
-#include "SkWriteBuffer.h"
-#include "SkString.h"
-#include "SkValue.h"
-#include "SkValueKeys.h"
-
-SkXfermode* SkLerpXfermode::Create(SkScalar scale) {
-    int scale256 = SkScalarRoundToInt(scale * 256);
-    if (scale256 >= 256) {
-        return SkXfermode::Create(SkXfermode::kSrc_Mode);
-    } else if (scale256 <= 0) {
-        return SkXfermode::Create(SkXfermode::kDst_Mode);
-    }
-    return new SkLerpXfermode(scale256);
-}
-
-SkLerpXfermode::SkLerpXfermode(unsigned scale256) : fScale256(scale256) {}
-
-void SkLerpXfermode::flatten(SkWriteBuffer& buffer) const {
-    buffer.writeUInt(fScale256);
-}
-
-SkFlattenable* SkLerpXfermode::CreateProc(SkReadBuffer& buffer) {
-    return new SkLerpXfermode(buffer.readUInt());
-}
-
-void SkLerpXfermode::xfer32(SkPMColor dst[], const SkPMColor src[], int count,
-                             const SkAlpha aa[]) const {
-    const int scale = fScale256;
-
-    if (aa) {
-        for (int i = 0; i < count; ++i) {
-            unsigned a = aa[i];
-            if (a) {
-                SkPMColor dstC = dst[i];
-                SkPMColor resC = SkFastFourByteInterp256(src[i], dstC, scale);
-                if (a < 255) {
-                    resC = SkFastFourByteInterp256(resC, dstC, a + (a >> 7));
-                }
-                dst[i] = resC;
-            }
-        }
-    } else {
-        for (int i = 0; i < count; ++i) {
-            dst[i] = SkFastFourByteInterp256(src[i], dst[i], scale);
-        }
-    }
-}
-
-void SkLerpXfermode::xfer16(uint16_t dst[], const SkPMColor src[], int count,
-                             const SkAlpha aa[]) const {
-    const int scale = fScale256;
-
-    if (aa) {
-        for (int i = 0; i < count; ++i) {
-            unsigned a = aa[i];
-            if (a) {
-                SkPMColor dstC = SkPixel16ToPixel32(dst[i]);
-                SkPMColor resC = SkFastFourByteInterp256(src[i], dstC, scale);
-                if (a < 255) {
-                    resC = SkFastFourByteInterp256(resC, dstC, a + (a >> 7));
-                }
-                dst[i] = SkPixel32ToPixel16(resC);
-            }
-        }
-    } else {
-        for (int i = 0; i < count; ++i) {
-            SkPMColor dstC = SkPixel16ToPixel32(dst[i]);
-            SkPMColor resC = SkFastFourByteInterp256(src[i], dstC, scale);
-            dst[i] = SkPixel32ToPixel16(resC);
-        }
-    }
-}
-
-void SkLerpXfermode::xferA8(SkAlpha dst[], const SkPMColor src[], int count,
-                             const SkAlpha aa[]) const {
-    const int scale = fScale256;
-
-    if (aa) {
-        for (int i = 0; i < count; ++i) {
-            unsigned a = aa[i];
-            if (a) {
-                unsigned dstA = dst[i];
-                unsigned resA = SkAlphaBlend(SkGetPackedA32(src[i]), dstA, scale);
-                if (a < 255) {
-                    resA = SkAlphaBlend(resA, dstA, a + (a >> 7));
-                }
-                dst[i] = resA;
-            }
-        }
-    } else {
-        for (int i = 0; i < count; ++i) {
-            dst[i] = SkAlphaBlend(SkGetPackedA32(src[i]), dst[i], scale);
-        }
-    }
-}
-
-#ifndef SK_IGNORE_TO_STRING
-void SkLerpXfermode::toString(SkString* str) const {
-    str->printf("SkLerpXfermode: scale: %g", fScale256 / 256.0);
-}
-#endif
-
-SkValue SkLerpXfermode::asValue() const {
-    auto value = SkValue::Object(SkValue::LerpXfermode);
-    value.set(SkValueKeys::LerpXfermode::kScale,
-              SkValue::FromF32(fScale256 / 256.0f));
-    return value;
-}
diff --git a/src/effects/SkToFromValue.cpp b/src/effects/SkToFromValue.cpp
index b981d1715e..cbb265b33f 100644
--- a/src/effects/SkToFromValue.cpp
+++ b/src/effects/SkToFromValue.cpp
@@ -6,7 +6,6 @@
  */
 
 #include "SkArithmeticMode.h"
-#include "SkLerpXfermode.h"
 #include "SkMatrix.h"
 #include "SkPixelXorXfermode.h"
 #include "SkToFromValue.h"
@@ -89,14 +88,6 @@ static bool from_value_ArithmeticXfermode(const SkValue& val,
     return true;
 }
 
-static bool from_value_LerpXfermode(const SkValue& val,
-                                    SkAutoTUnref<SkXfermode>* dst) {
-    float scale;
-    REQUIRE(getT(val, SkValueKeys::LerpXfermode::kScale, &scale));
-    dst->reset(SkLerpXfermode::Create(scale));
-    return true;
-}
-
 static bool from_value_PixelXorXfermode(const SkValue& val,
                                         SkAutoTUnref<SkXfermode>* dst) {
     uint32_t opColor;
@@ -118,7 +109,6 @@ template<> bool SkFromValue< SkAutoTUnref<SkXfermode> >(
     switch (val.type()) {
         case SkValue::DefaultXfermode:    return from_value_DefaultXfermode(val, dst);
         case SkValue::ArithmeticXfermode: return from_value_ArithmeticXfermode(val, dst);
-        case SkValue::LerpXfermode:       return from_value_LerpXfermode(val, dst);
         case SkValue::PixelXorXfermode:   return from_value_PixelXorXfermode(val, dst);
         case SkValue::ProcCoeffXfermode:  return from_value_ProcCoeffXfermode(val, dst);
         default:                          REQUIRE(false);