win: Remove __alignof workaround, no longer needed.

No intended behavior change.

BUG=none

Review URL: https://codereview.chromium.org/1071513003

Cr-Commit-Position: refs/heads/master@{#324272}

base/compiler_specific.h

@@ -128,13 +128,11 @@
 #define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
 #endif
 
-// Return the byte alignment of the given type (available at compile time).  Use
-// sizeof(type) prior to checking __alignof to workaround Visual C++ bug:
-// http://goo.gl/isH0C
+// Return the byte alignment of the given type (available at compile time).
 // Use like:
 //   ALIGNOF(int32)  // this would be 4
 #if defined(COMPILER_MSVC)
-#define ALIGNOF(type) (sizeof(type) - sizeof(type) + __alignof(type))
+#define ALIGNOF(type) __alignof(type)
 #elif defined(COMPILER_GCC)
 #define ALIGNOF(type) __alignof__(type)
 #endif