remove redundant/deprecated TwoPointRadial gradiet -- use TwoPointConical

This CL derived from https://codereview.chromium.org/1114243005/

BUG=skia:

Review URL: https://codereview.chromium.org/1117423003
diff --git a/samplecode/SampleSlides.cpp b/samplecode/SampleSlides.cpp
index 6899fc1..83e91bb 100644
--- a/samplecode/SampleSlides.cpp
+++ b/samplecode/SampleSlides.cpp
@@ -197,13 +197,13 @@
     return SkGradientShader::CreateSweep(center.fX, center.fY, data.fColors, data.fPos, data.fCount);
 }
 
-static SkShader* Make2Radial(const SkPoint pts[2], const GradData& data, SkShader::TileMode tm) {
+static SkShader* Make2Conical(const SkPoint pts[2], const GradData& data, SkShader::TileMode tm) {
     SkPoint center0, center1;
     center0.set(SkScalarAve(pts[0].fX, pts[1].fX),
                 SkScalarAve(pts[0].fY, pts[1].fY));
     center1.set(SkScalarInterp(pts[0].fX, pts[1].fX, SkIntToScalar(3)/5),
                 SkScalarInterp(pts[0].fY, pts[1].fY, SkIntToScalar(1)/4));
-    return SkGradientShader::CreateTwoPointRadial(
+    return SkGradientShader::CreateTwoPointConical(
                                                   center1, (pts[1].fX - pts[0].fX) / 7,
                                                   center0, (pts[1].fX - pts[0].fX) / 2,
                                                   data.fColors, data.fPos, data.fCount, tm);
@@ -211,7 +211,7 @@
 
 typedef SkShader* (*GradMaker)(const SkPoint pts[2], const GradData& data, SkShader::TileMode tm);
 static const GradMaker gGradMakers[] = {
-    MakeLinear, MakeRadial, MakeSweep, Make2Radial
+    MakeLinear, MakeRadial, MakeSweep, Make2Conical
 };
 
 static void gradient_slide(SkCanvas* canvas) {