Revert "mark SkRasterPipelineBlitter final"

This reverts commit 317a1857f8.

Reason for revert: Valgrind requires reverting ancestor commit.

Original change's description:
> mark SkRasterPipelineBlitter final
> 
> This devirtualizes the call from blitAntiH to blitH,
> and makes sure no future self calls will be virtual.
> 
> Change-Id: I2a277bbc1450a96e07794791792d59e5f806bde0
> Reviewed-on: https://skia-review.googlesource.com/17418
> Commit-Queue: Mike Klein <mtklein@chromium.org>
> Reviewed-by: Mike Klein <mtklein@chromium.org>
> 

TBR=mtklein@chromium.org,herb@google.com,reed@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: Ic726fd6b9bf18c397812ecc256353ab4a0a336c5
Reviewed-on: https://skia-review.googlesource.com/17522
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

src/core/SkRasterPipelineBlitter.cpp

@@ -18,7 +18,7 @@
 #include "SkUtils.h"
 #include "../jumper/SkJumper.h"
 
-class SkRasterPipelineBlitter final : public SkBlitter {
+class SkRasterPipelineBlitter : public SkBlitter {
 public:
     // Create using paint.getShader() or paint.getColor() if there is no shader.
     // If there's a shader, we will modulate the shader color by the paint alpha.