libwebp: cherry-pick arm gcc-4.9 fix

third_party/libwebp/dsp/lossless.c

Index: third_party/libwebp/dsp/lossless.c
diff --git a/third_party/libwebp/dsp/lossless.c b/third_party/libwebp/dsp/lossless.c
index 84e207840515f494e0b4f81d9f7aba53297f132c..b7e02c25974b847809c3cf300ee4a998f40d8536 100644
--- a/third_party/libwebp/dsp/lossless.c
+++ b/third_party/libwebp/dsp/lossless.c
@@ -450,12 +450,21 @@ static WEBP_INLINE uint32_t ClampedAddSubtractHalf(uint32_t c0, uint32_t c1,
   return ((uint32_t)a << 24) | (r << 16) | (g << 8) | b;
 }
 
-static WEBP_INLINE int Sub3(int a, int b, int c) {
+// gcc-4.9 on ARM generates incorrect code in Select() when Sub3() is inlined.
+#if defined(__arm__) && LOCAL_GCC_VERSION == 0x409
+# define LOCAL_INLINE __attribute__ ((noinline))
+#else
+# define LOCAL_INLINE WEBP_INLINE
+#endif
+
+static LOCAL_INLINE int Sub3(int a, int b, int c) {
   const int pb = b - c;
   const int pa = a - c;
   return abs(pb) - abs(pa);
 }
 
+#undef LOCAL_INLINE
+
 static WEBP_INLINE uint32_t Select(uint32_t a, uint32_t b, uint32_t c) {
   const int pa_minus_pb =
       Sub3((a >> 24)       , (b >> 24)       , (c >> 24)       ) +