ubsan shift fixes

src/images/SkImageDecoder_libico.cpp

Index: src/images/SkImageDecoder_libico.cpp
diff --git a/src/images/SkImageDecoder_libico.cpp b/src/images/SkImageDecoder_libico.cpp
index e8b4bc5c316cbe1b7fd587b85e5abdd672bb4f8f..cb21b6906e9bd849e039339905d122cc01ef2ca0 100644
--- a/src/images/SkImageDecoder_libico.cpp
+++ b/src/images/SkImageDecoder_libico.cpp
@@ -32,8 +32,8 @@ private:
 //read in Intel order, and return an integer
 
 #define readByte(buffer,begin) buffer[begin]
-#define read2Bytes(buffer,begin) buffer[begin]+(buffer[begin+1]<<8)
-#define read4Bytes(buffer,begin) buffer[begin]+(buffer[begin+1]<<8)+(buffer[begin+2]<<16)+(buffer[begin+3]<<24)
+#define read2Bytes(buffer,begin) buffer[begin]+SkLeftShift(buffer[begin+1],8)
+#define read4Bytes(buffer,begin) buffer[begin]+SkLeftShift(buffer[begin+1],8)+SkLeftShift(buffer[begin+2],16)+SkLeftShift(buffer[begin+3],24)
 
 /////////////////////////////////////////////////////////////////////////////////////////