remove one place we read from gpu key in effects

BUG=skia:

Review URL: https://codereview.chromium.org/761643002
diff --git a/src/effects/gradients/SkTwoPointRadialGradient.cpp b/src/effects/gradients/SkTwoPointRadialGradient.cpp
index 3680665..f4bcc2c 100644
--- a/src/effects/gradients/SkTwoPointRadialGradient.cpp
+++ b/src/effects/gradients/SkTwoPointRadialGradient.cpp
@@ -568,14 +568,14 @@
 }
 
 void GrGLRadial2Gradient::emitCode(GrGLFPBuilder* builder,
-                                   const GrFragmentProcessor&,
+                                   const GrFragmentProcessor& fp,
                                    const GrProcessorKey& key,
                                    const char* outputColor,
                                    const char* inputColor,
                                    const TransformedCoordsArray& coords,
                                    const TextureSamplerArray& samplers) {
-    uint32_t baseKey = key.get32(0);
-    this->emitUniforms(builder, baseKey);
+    const GrGradientEffect& ge = fp.cast<GrGradientEffect>();
+    this->emitUniforms(builder, ge);
     fParamUni = builder->addUniformArray(GrGLProgramBuilder::kFragment_Visibility,
                                          kFloat_GrSLType, "Radial2FSParams", 6);
 
@@ -638,7 +638,7 @@
         t.printf("-%s / %s", cName.c_str(), bVar.c_str());
     }
 
-    this->emitColor(builder, t.c_str(), baseKey, outputColor, inputColor, samplers);
+    this->emitColor(builder, ge, t.c_str(), outputColor, inputColor, samplers);
 }
 
 void GrGLRadial2Gradient::setData(const GrGLProgramDataManager& pdman,