Fixed bug in large switch tables on arm.

src/constants-arm.h

Index: src/constants-arm.h
diff --git a/src/constants-arm.h b/src/constants-arm.h
index 46ddb1534938ca3cdbae0f3e31f31bee7201d173..f55396380ac756be0608c4ce34621efcc0e691f2 100644
--- a/src/constants-arm.h
+++ b/src/constants-arm.h
@@ -129,6 +129,7 @@ class Instr {
  public:
   enum {
     kInstrSize = 4,
+    kInstrSizeLog2 = 2,
     kPCReadOffset = 8
   };