Shorten the namespace and re-normalize include guards.

Change-Id: I93af4c1f19edf31098abd20ded1fcca6c5d83854
diff --git a/src/logging.h b/src/logging.h
index c1896e9..ccab249 100644
--- a/src/logging.h
+++ b/src/logging.h
@@ -11,8 +11,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#ifndef ART_LOGGING_H_
-#define ART_LOGGING_H_
+#ifndef ART_SRC_LOGGING_H_
+#define ART_SRC_LOGGING_H_
 
 #include <cstdlib>
 #include <iostream>  // NOLINT
@@ -99,4 +99,4 @@
   DISALLOW_COPY_AND_ASSIGN(LogMessageFatal);
 };
 
-#endif  // ART_LOGGING_H_
+#endif  // ART_SRC_LOGGING_H_