Remove a warning.

git-svn-id: http://skia.googlecode.com/svn/trunk@1303 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gpu/src/GrGLProgram.cpp b/gpu/src/GrGLProgram.cpp
index f89de9b..adffa35 100644
--- a/gpu/src/GrGLProgram.cpp
+++ b/gpu/src/GrGLProgram.cpp
@@ -216,8 +216,8 @@
 static void addColorFilter(GrStringBuilder& FSCode, const char * outputVar,
             SkXfermode::Mode colorFilterXfermode, const char* dstColor) {
     SkXfermode::Coeff srcCoeff, dstCoeff;
-    bool success = SkXfermode::ModeAsCoeff(colorFilterXfermode,
-            &srcCoeff, &dstCoeff);
+    SkDEBUGCODE(bool success =)
+    SkXfermode::ModeAsCoeff(colorFilterXfermode, &srcCoeff, &dstCoeff);
     // We currently do not handle modes that cannot be represented as
     // coefficients.
     GrAssert(success);