Move shader compiling to ProgramBuilder and various ShaderBuilder cleanups.

src/gpu/gl/GrGLGpu.h

Index: src/gpu/gl/GrGLGpu.h
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index 396d488174dfdabdcf254c26815db1a15a818bc8..c10d79e744ff128d6771b3c7773b7def8623a732 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -128,6 +128,11 @@ public:
     bool isTestingOnlyBackendTexture(GrBackendObject id) const override;
     void deleteTestingOnlyBackendTexture(GrBackendObject id) const override;
 
+    /** If texture swizzling is available using tex parameters then it is preferred over mangling
+        the generated shader code. This potentially allows greater reuse of cached shaders. */
+    static const GrGLenum* GetTexParamSwizzle(GrPixelConfig config, const GrGLCaps& caps);
+
+
 private:
     GrGLGpu(GrGLContext* ctx, GrContext* context);