Fixed crash when RunInSeriesFP's color input is nil

src/gpu/GrFragmentProcessor.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 "GrFragmentProcessor.h"
 #include "GrCoordTransform.h"
 #include "GrInvariantOutput.h"
@@ skipping 292 matching lines @@
                 this->registerChildProcessor(std::move(children[i]));
             }
         }
 
         const char* name() const override { return "Series"; }
 
         GrGLSLFragmentProcessor* onCreateGLSLInstance() const override {
             class GLFP : public GrGLSLFragmentProcessor {
             public:
                 void emitCode(EmitArgs& args) override {
-                    SkString input(args.fInputColor);
-                    for (int i = 0; i < this->numChildProcessors() - 1; ++i) {
-                        SkString temp;
+                    // First guy's input might be nil.
+                    SkString temp("out0");
+                    this->emitChild(0, args.fInputColor, &temp, args);
+                    SkString input = temp;
+                    for (int i = 1; i < this->numChildProcessors() - 1; ++i) {
                         temp.printf("out%d", i);
                         this->emitChild(i, input.c_str(), &temp, args);
                         input = temp;
                     }
                     // Last guy writes to our output variable.
                     this->emitChild(this->numChildProcessors() - 1, input.c_str(), args);
                 }
             };
             return new GLFP;
         }
@@ skipping 42 matching lines @@
     } else {
         series += firstIdx;
         cnt -= firstIdx;
     }
 
     if (1 == cnt) {
         return series[0];
     }
     return sk_sp<GrFragmentProcessor>(new SeriesFragmentProcessor(series, cnt));
 }