Re-land "converted GrCircleBlurFragmentProcessor to sksl"

This reverts commit 818ac5a00dfd570d2b291b7524a70ecd4ef55770.

Bug: skia:
Change-Id: I9bd8a06bd2dbb40bd261d64d6d04daf864bc00a5
Reviewed-on: https://skia-review.googlesource.com/22075
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
diff --git a/src/sksl/SkSLCPPCodeGenerator.h b/src/sksl/SkSLCPPCodeGenerator.h
index c7388ad..0f6da5f 100644
--- a/src/sksl/SkSLCPPCodeGenerator.h
+++ b/src/sksl/SkSLCPPCodeGenerator.h
@@ -39,6 +39,10 @@
 
     void writeVariableReference(const VariableReference& ref) override;
 
+    String getSamplerHandle(const Variable& var);
+
+    void writeFunctionCall(const FunctionCall& c) override;
+
     void writeFunction(const FunctionDefinition& f) override;
 
     void writeSetting(const Setting& s) override;