Revert of remove unused (by clients) SkUnitMapper

src/core/SkValidatingReadBuffer.cpp

Index: src/core/SkValidatingReadBuffer.cpp
diff --git a/src/core/SkValidatingReadBuffer.cpp b/src/core/SkValidatingReadBuffer.cpp
index 96f20a24833b7e23b7e34d54aa58fa28f45a848d..0112f18ec44d5b922d9a0e4455e6975b371577df 100644
--- a/src/core/SkValidatingReadBuffer.cpp
+++ b/src/core/SkValidatingReadBuffer.cpp
@@ -273,15 +273,3 @@
     }
     return obj;
 }
-
-void SkValidatingReadBuffer::skipFlattenable() {
-    SkString name;
-    this->readString(&name);
-    if (fError) {
-        return;
-    }
-    uint32_t sizeRecorded = this->readUInt();
-    this->skip(sizeRecorded);
-}
-
-