Test that GrFragmentProcessors work without input colors.

src/gpu/effects/GrConstColorProcessor.cpp

Index: src/gpu/effects/GrConstColorProcessor.cpp
diff --git a/src/gpu/effects/GrConstColorProcessor.cpp b/src/gpu/effects/GrConstColorProcessor.cpp
index 95a4081d4f7df2421435f51cf9d362f7e15c07ee..627139fa413d2f717c7e77cb2149f5060b3b0583 100644
--- a/src/gpu/effects/GrConstColorProcessor.cpp
+++ b/src/gpu/effects/GrConstColorProcessor.cpp
@@ -19,7 +19,11 @@ public:
         fColorUniform = args.fBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                             kVec4f_GrSLType, kMedium_GrSLPrecision, "constantColor",
                                             &colorUni);
-        switch (args.fFp.cast<GrConstColorProcessor>().inputMode()) {
+        GrConstColorProcessor::InputMode mode = args.fFp.cast<GrConstColorProcessor>().inputMode();
+        if (!args.fInputColor) {
+            mode = GrConstColorProcessor::kIgnore_InputMode;
+        }
+        switch (mode) {
             case GrConstColorProcessor::kIgnore_InputMode:
                 fsBuilder->codeAppendf("%s = %s;", args.fOutputColor, colorUni);
                 break;