formalize named picture versions

src/core/SkShader.cpp

Index: src/core/SkShader.cpp
diff --git a/src/core/SkShader.cpp b/src/core/SkShader.cpp
index 6a418b6b4578eb6c2be004f5d809dcb984ff9b4b..9484db59c18837ac6feaa767cbff03a05cc78613 100644
--- a/src/core/SkShader.cpp
+++ b/src/core/SkShader.cpp
@@ -255,7 +255,7 @@ bool SkColorShader::isOpaque() const {
 SkColorShader::SkColorShader(SkReadBuffer& b) : INHERITED(b) {
     // V25_COMPATIBILITY_CODE We had a boolean to make the color shader inherit the paint's
     // color. We don't support that any more.
-    if (b.pictureVersion() < 26 && 0 != b.pictureVersion()) {
+    if (b.isVersionLT(SkReadBuffer::kColorShaderNoBool_Version)) {
         if (b.readBool()) {
             SkDEBUGFAIL("We shouldn't have pictures that recorded the inherited case.");
             fColor = SK_ColorWHITE;