Simplify SkPDFShader class. Now invalid objects are never created.

src/pdf/SkPDFShader.h

Index: src/pdf/SkPDFShader.h
diff --git a/src/pdf/SkPDFShader.h b/src/pdf/SkPDFShader.h
index e0abff8f68388324128cbe15bfebfc4d49540bc2..ba10243ff435cf488207e9fc59f89bfe12363cf8 100644
--- a/src/pdf/SkPDFShader.h
+++ b/src/pdf/SkPDFShader.h
@@ -55,13 +55,10 @@ protected:
     // CanonicalShadersMutex() should already be acquired.
     // This also takes ownership of shaderState.
     static SkPDFObject* GetPDFShaderByState(State* shaderState);
-    static SkPDFObject* AddToCanonIfValid(SkPDFShader*);
-    static void RemoveFromCanonIfValid(SkPDFShader*);
 
     SkPDFShader(State*);
     virtual ~SkPDFShader();
 
-    virtual bool isValid() = 0;
     virtual SkPDFObject* toPDFObject() = 0;

[mtklein, 2015/01/22 18:32:41]

Uh, wait, what's really going on here?  Is SkPDFShader not an SkPDFObject, but
all its subclasses are?  That seems bad.

 };