Add GrShaderFlags enum

Replaces GrGLSLUniformHandler::ShaderVisibility with GrShaderFlags.

BUG=skia:
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Review URL: https://codereview.chromium.org/1684063006
diff --git a/src/gpu/effects/GrMatrixConvolutionEffect.cpp b/src/gpu/effects/GrMatrixConvolutionEffect.cpp
index a7f829e..ac7889d 100644
--- a/src/gpu/effects/GrMatrixConvolutionEffect.cpp
+++ b/src/gpu/effects/GrMatrixConvolutionEffect.cpp
@@ -40,19 +40,19 @@
     int kHeight = mce.kernelSize().height();
 
     GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
-    fImageIncrementUni = uniformHandler->addUniform(GrGLSLUniformHandler::kFragment_Visibility,
+    fImageIncrementUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                     kVec2f_GrSLType, kDefault_GrSLPrecision,
                                                     "ImageIncrement");
-    fKernelUni = uniformHandler->addUniformArray(GrGLSLUniformHandler::kFragment_Visibility,
+    fKernelUni = uniformHandler->addUniformArray(kFragment_GrShaderFlag,
                                                  kFloat_GrSLType, kDefault_GrSLPrecision,
                                                  "Kernel",
                                                  kWidth * kHeight);
-    fKernelOffsetUni = uniformHandler->addUniform(GrGLSLUniformHandler::kFragment_Visibility,
+    fKernelOffsetUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                   kVec2f_GrSLType, kDefault_GrSLPrecision,
                                                   "KernelOffset");
-    fGainUni = uniformHandler->addUniform(GrGLSLUniformHandler::kFragment_Visibility,
+    fGainUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                           kFloat_GrSLType, kDefault_GrSLPrecision, "Gain");
-    fBiasUni = uniformHandler->addUniform(GrGLSLUniformHandler::kFragment_Visibility,
+    fBiasUni = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                           kFloat_GrSLType, kDefault_GrSLPrecision, "Bias");
 
     const char* kernelOffset = uniformHandler->getUniformCStr(fKernelOffsetUni);