Add ALIGNAS and ALIGNOF macros to ensure proper alignment of StaticMemorySingletonTraits

base/compiler_specific.h

Index: base/compiler_specific.h
diff --git a/base/compiler_specific.h b/base/compiler_specific.h
index 0d9346096e87ba49435b6378d3408676dcb2ff9d..9e65ae4d4824d0e1ddccb206e8113949daf33fe8 100644
--- a/base/compiler_specific.h
+++ b/base/compiler_specific.h
@@ -105,6 +105,25 @@
 #define NOINLINE
 #endif
 
+// Specify memory alignment for structs, classes, etc.
+// Use like:
+//   class ALIGNAS(16) MyClass { ... }
+//   ALIGNAS(16) int array[4];
+#if defined(COMPILER_MSVC)
+#define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
+#elif defined(COMPILER_GCC)
+#define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
+#endif
+
+// 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) __alignof(type)
+#elif defined(COMPILER_GCC)
+#define ALIGNOF(type) __alignof__(type)
+#endif
+
 // Annotate a virtual method indicating it must be overriding a virtual
 // method in the parent class.
 // Use like: