Revert of Update feSpotLight to match spec (patchset #2 id:20001 of https://codereview.chromium.org/1403403003/ )

Reason for revert:
re-land once layout test have been disabled (so they can be rebased)

Original issue's description:
> Update feSpotLight to match spec
>
> This change updates feSpotLight to match the spec via two changes:
>
> 1) specularExponent is ignored if the spotlight has no coneAngle (GPU
>    bug only). This change updates the GPU path so that it matches the
>    CPU path and the spec in this regard.
>
> 2) specularExponent is clamped to the 1-128 range. The spec does not
>    specify a clamp for the specularExponent attribute of feSpotLight.
>    Note that the spec *does* specify this clamp for the
>    specularExponent attribute of feSpecularLighting. It looks like we
>    incorrectly applied this to both specularExponent attributes.
>
>    This change (along with a parallel change in Blink) allows us to pass
>    the SVG filter effects conformance test here:
>    http://www.w3.org/Graphics/SVG/Test/20110816/harness/htmlObject/filters-light-01-f.html
>
>    Additionally, this brings our behavior in line with Safari and Edge’s
>    behavior on this filter.
>
> Two new cases were added to gm/lighting.cpp to catch these issues:
> - The existing spotlight case exercised the path where our specular
>   exponent was between 1-128 and had a limiting cone angle.
> - The first new spotlight case exercises the path where our specular
>   exponent is between 1-128 and we do not have a limiting cone angle.
> - The second new spotlight case exercises the path where the specular
>   exponent is not within the 1-128 range, to ensure that we don’t
>   incorrectly clip to this range.
>
> BUG=472849
>
> Committed: https://skia.googlesource.com/skia/+/c84ccb070258db2803a9e8f532bfe7239a737063

TBR=senorblanco@google.com,senorblanco@chromium.org,bsalomon@google.com,ericrk@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=472849

Review URL: https://codereview.chromium.org/1417463006

1 files changed, 13 insertions, 5 deletions

diff --git a/src/effects/SkLightingImageFilter.cpp b/src/effects/SkLightingImageFilter.cpp
index f0f2c66d6f..199bb4d684 100644
--- a/src/effects/SkLightingImageFilter.cpp
+++ b/src/effects/SkLightingImageFilter.cpp
@@ -682,7 +682,7 @@ class GrGLLight;
 
 class SkImageFilterLight : public SkRefCnt {
 public:
-
+    
 
     enum LightType {
         kDistant_LightType,
@@ -819,8 +819,8 @@ public:
         // Use X scale and Y scale on Z and average the result
         SkPoint locationZ = SkPoint::Make(fLocation.fZ, fLocation.fZ);
         matrix.mapVectors(&locationZ, 1);
-        SkPoint3 location = SkPoint3::Make(location2.fX,
-                                           location2.fY,
+        SkPoint3 location = SkPoint3::Make(location2.fX, 
+                                           location2.fY, 
                                            SkScalarAve(locationZ.fX, locationZ.fY));
         return new SkPointLight(location, color());
     }
@@ -854,7 +854,7 @@ public:
      : INHERITED(color),
        fLocation(location),
        fTarget(target),
-       fSpecularExponent(specularExponent)
+       fSpecularExponent(SkScalarPin(specularExponent, kSpecularExponentMin, kSpecularExponentMax))
     {
        fS = target - location;
        fast_normalize(&fS);
@@ -984,6 +984,9 @@ protected:
     }
 
 private:
+    static const SkScalar kSpecularExponentMin;
+    static const SkScalar kSpecularExponentMax;
+
     SkPoint3 fLocation;
     SkPoint3 fTarget;
     SkScalar fSpecularExponent;
@@ -995,6 +998,11 @@ private:
     typedef SkImageFilterLight INHERITED;
 };
 
+// According to the spec, the specular term should be in the range [1, 128] :
+// http://www.w3.org/TR/SVG/filters.html#feSpecularLightingSpecularExponentAttribute
+const SkScalar SkSpotLight::kSpecularExponentMin = 1.0f;
+const SkScalar SkSpotLight::kSpecularExponentMax = 128.0f;
+
 ///////////////////////////////////////////////////////////////////////////////
 
 void SkImageFilterLight::flattenLight(SkWriteBuffer& buffer) const {
@@ -1985,7 +1993,7 @@ void GrGLSpotLight::emitLightColor(GrGLFPBuilder* builder,
     lightColorBody.appendf("\t\treturn %s * scale * (cosAngle - %s) * %s;\n",
                            color, cosOuter, coneScale);
     lightColorBody.appendf("\t}\n");
-    lightColorBody.appendf("\treturn %s * scale;\n", color);
+    lightColorBody.appendf("\treturn %s;\n", color);
     GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
     fsBuilder->emitFunction(kVec3f_GrSLType,
                             "lightColor",