Introduce CPU(ARM64)

BUG=354405
R=ager@chromium.org

Review URL: https://codereview.chromium.org/209843002

git-svn-id: svn://svn.chromium.org/blink/trunk@169846 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/wtf/CPU.h

@@ -180,4 +180,10 @@
 
 #endif /* ARM */
 
+/* CPU(ARM64) - AArch64 64-bit */
+#if defined(__aarch64__)
+#define WTF_CPU_ARM64 1
+#define WTF_CPU_64BIT 1
+#endif
+
 #endif /* WTF_CPU_h */