Cleanup include guards:

src/arm/codegen-arm.h

Index: src/arm/codegen-arm.h
diff --git a/src/arm/codegen-arm.h b/src/arm/codegen-arm.h
index 48b92eab55413984142c1b501c0ffdea30d98df0..a5f77fe6956ddd67893d7dd4925e83eb657e6874 100644
--- a/src/arm/codegen-arm.h
+++ b/src/arm/codegen-arm.h
@@ -25,8 +25,8 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-#ifndef V8_CODEGEN_ARM_H_
-#define V8_CODEGEN_ARM_H_
+#ifndef V8_ARM_CODEGEN_ARM_H_
+#define V8_ARM_CODEGEN_ARM_H_
 
 namespace v8 { namespace internal {
 
@@ -443,4 +443,4 @@ class CodeGenerator: public AstVisitor {
 
 } }  // namespace v8::internal
 
-#endif  // V8_CODEGEN_ARM_H_
+#endif  // V8_ARM_CODEGEN_ARM_H_