adding new GM to demostrate new shadows

src/core/SkLightingShader.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapProcShader.h"
 #include "SkBitmapProcState.h"
 #include "SkColor.h"
@@ skipping 146 matching lines @@
 
         // fuse all ambient lights into a single one
         fAmbientColor.set(0.0f, 0.0f, 0.0f);
         for (int i = 0; i < lights->numLights(); ++i) {
             if (SkLights::Light::kAmbient_LightType == lights->light(i).type()) {
                 fAmbientColor += lights->light(i).color();
             } else {
                 // TODO: handle more than one of these
                 fLightColor = lights->light(i).color();
                 fLightDir = lights->light(i).dir();
+                // get the handle to the shadow map if there is one
             }
         }
 
         this->registerChildProcessor(std::move(normalFP));
         this->initClassID<LightingFP>();
     }
 
     class GLSLLightingFP : public GrGLSLFragmentProcessor {
     public:
         GLSLLightingFP() {
@@ skipping 26 matching lines @@
             fragBuilder->codeAppend("vec4 diffuseColor = ");
             fragBuilder->appendTextureLookupAndModulate(args.fInputColor, args.fTexSamplers[0],
                                                 args.fCoords[0].c_str(),
                                                 args.fCoords[0].getType());
             fragBuilder->codeAppend(";");
 
             SkString dstNormalName("dstNormal");
             this->emitChild(0, nullptr, &dstNormalName, args);
 
             fragBuilder->codeAppendf("vec3 normal = %s.xyz;", dstNormalName.c_str());
+
+            // TODO: make this a loop and modulate the contribution from each light
+            // based on the shadow map
             fragBuilder->codeAppendf("float NdotL = clamp(dot(normal, %s), 0.0, 1.0);",
                                      lightDirUniName);
             // diffuse light
             fragBuilder->codeAppendf("vec3 result = %s*diffuseColor.rgb*NdotL;", lightColorUniName);
             // ambient light
             fragBuilder->codeAppendf("result += %s;", ambientColorUniName);
             fragBuilder->codeAppendf("%s = vec4(result.rgb, diffuseColor.a);", args.fOutputColor);
         }
 
         static void GenKey(const GrProcessor& proc, const GrGLSLCaps&,
@@ skipping 425 matching lines @@
             invNormRotation, diffLocalM, normLocalM, std::move(normalSource));
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkLightingShader)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkLightingShaderImpl)
 SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
 
 ///////////////////////////////////////////////////////////////////////////////