Update feSpotLight to match spec

src/effects/SkLightingImageFilter.cpp

Index: src/effects/SkLightingImageFilter.cpp
diff --git a/src/effects/SkLightingImageFilter.cpp b/src/effects/SkLightingImageFilter.cpp
index 4265f6e1e53c23137f5ca9db523169c44bde5c40..ec7d72fe2db0c242723343601a8cf853e982fe03 100644
--- a/src/effects/SkLightingImageFilter.cpp
+++ b/src/effects/SkLightingImageFilter.cpp
@@ -855,7 +855,7 @@ public:
      : INHERITED(color),
        fLocation(location),
        fTarget(target),
-       fSpecularExponent(SkScalarPin(specularExponent, kSpecularExponentMin, kSpecularExponentMax))

[Stephen White, 2015/10/16 15:03:10]

Although it may not be spec-correct, this was added by sugoi@ back in
https://chromiumcodereview.appspot.com/23533042/ in order to fix a fuzzer issue.
According to that change, large negative values were a problem, presumably
generating near-zero scale when passed to pow(). That said, I tried the unit
test in debug with your change, and it didn't assert, so maybe we're ok.

(By way of explanation, the fuzzer is there to test Skia when run cross-process,
which we do for accelerated filters. Even if Blink applies the correct limits,
we need to protect Skia against a compromised renderer process giving arbitrary
values.)

Also, this seems to be the last use of these min/max constants. We should either
apply them to "shininess" as the spec suggests, or remove them.

[ericrk, 2015/10/16 18:36:23]

Per offline discussion - going to remove and see if fuzz gets mad - will add a
less restrictive limit back if it does. removing constant for now.

+       fSpecularExponent(specularExponent)
     {
        fS = target - location;
        fast_normalize(&fS);
@@ -1996,7 +1996,7 @@ 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;\n", color);
+    lightColorBody.appendf("\treturn %s * scale;\n", color);
     GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
     fsBuilder->emitFunction(kVec3f_GrSLType,
                             "lightColor",