Remove unused (by clients) SkUnitMapper (https://codereview.chromium.org/283273002/)

include/core/SkReadBuffer.h

Index: include/core/SkReadBuffer.h
diff --git a/include/core/SkReadBuffer.h b/include/core/SkReadBuffer.h
index 4da27d4fe0c6902de0a908a3637ebcfe120d2d48..e962234ddb6bccf06f2b55f19551cffce2df6115 100644
--- a/include/core/SkReadBuffer.h
+++ b/include/core/SkReadBuffer.h
@@ -23,7 +23,6 @@
 #include "SkReader32.h"
 #include "SkRefCnt.h"
 #include "SkShader.h"
-#include "SkUnitMapper.h"
 #include "SkWriteBuffer.h"
 #include "SkXfermode.h"
 
@@ -45,6 +44,7 @@ public:
         kGradientFlippedFlag_Version       = 24,
         kDashWritesPhaseIntervals_Version  = 25,
         kColorShaderNoBool_Version         = 26,
+        kNoUnitMappers_Version             = 27,
     };
 
     /**
@@ -121,9 +121,13 @@ public:
     SkPixelRef*    readPixelRef()    { return this->readFlattenable<SkPixelRef>(); }
     SkRasterizer*  readRasterizer()  { return this->readFlattenable<SkRasterizer>(); }
     SkShader*      readShader()      { return this->readFlattenable<SkShader>(); }
-    SkUnitMapper*  readUnitMapper()  { return this->readFlattenable<SkUnitMapper>(); }
     SkXfermode*    readXfermode()    { return this->readFlattenable<SkXfermode>(); }
 
+    /**
+     *  Like readFlattenable() but explicitly just skips the data that was written for the
+     *  flattenable (or the sentinel that there wasn't one).
+     */
+    virtual void skipFlattenable();
 
     // binary data and arrays
     virtual bool readByteArray(void* value, size_t size);