Put clear and discard into GrBatch.

Review URL: https://codereview.chromium.org/1293563003
diff --git a/src/core/SkStringUtils.h b/src/core/SkStringUtils.h
index 2839ac2..fd158c3 100644
--- a/src/core/SkStringUtils.h
+++ b/src/core/SkStringUtils.h
@@ -35,4 +35,7 @@
     SkAppendScalar(str, value, kHex_SkScalarAsStringType);
 }
 
+/** Indents every non-empty line of the string by tabCnt tabs */
+SkString SkTabString(const SkString& string, int tabCnt);
+
 #endif