Fix compilation error when building with clang on Linux.

src/effects/gradients/SkGradientShader.cpp

Index: src/effects/gradients/SkGradientShader.cpp
diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index 38e9210cb34c2addbf73f82e359c0dd290f07d6b..ada98590176dad65420c58b5cdf19f5107e6c36d 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -484,18 +484,6 @@ static inline int SkFixedToFFFF(SkFixed x) {
     return x - (x >> 16);
 }
 
-static inline U16CPU bitsTo16(unsigned x, const unsigned bits) {
-    SkASSERT(x < (1U << bits));
-    if (6 == bits) {
-        return (x << 10) | (x << 4) | (x >> 2);
-    }
-    if (8 == bits) {
-        return (x << 8) | x;
-    }
-    sk_throw();
-    return 0;
-}
-
 const uint16_t* SkGradientShaderBase::GradientShaderCache::getCache16() {
     SkOnce(&fCache16Inited, &fCache16Mutex, SkGradientShaderBase::GradientShaderCache::initCache16,
            this);