Revert of Add gpu implementation of OverdrawXfermode

src/gpu/glsl/GrGLSLXferProcessor.h

Index: src/gpu/glsl/GrGLSLXferProcessor.h
diff --git a/src/gpu/glsl/GrGLSLXferProcessor.h b/src/gpu/glsl/GrGLSLXferProcessor.h
index 37e684fcde320b84a0019b62f4e4d74e4c3e0ea6..ed8099b6f307dedf121ede0a4ec2c2aaf3566278 100644
--- a/src/gpu/glsl/GrGLSLXferProcessor.h
+++ b/src/gpu/glsl/GrGLSLXferProcessor.h
@@ -68,14 +68,6 @@
      */
     void setData(const GrGLSLProgramDataManager& pdm, const GrXferProcessor& xp);
 
-protected:
-    static void DefaultCoverageModulation(GrGLSLXPFragmentBuilder* fragBuilder,
-                                          const char* srcCoverage,
-                                          const char* dstColor,
-                                          const char* outColor,
-                                          const char* outColorSecondary,
-                                          const GrXferProcessor& proc);
-
 private:
     /**
      * Called by emitCode() when the XP will not be performing a dst read. This method is