drm_hwcomposer: Add tracing for the main functions

This will help the profiling efforts, now that all the low-hanging
fruit is gone.

BUG=none
TEST=run systrace, see tracing

Change-Id: I9a149afdea8b84837c19f8e224ce8a7e2db1dd9a
diff --git a/drmcompositor.cpp b/drmcompositor.cpp
index dc4bfe8..0c6d445 100644
--- a/drmcompositor.cpp
+++ b/drmcompositor.cpp
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+#define ATRACE_TAG ATRACE_TAG_GRAPHICS
 #define LOG_TAG "hwc-drm-compositor"
 
 #include "drmcompositor.h"
@@ -25,6 +26,7 @@
 #include <sstream>
 #include <stdlib.h>
 #include <time.h>
+#include <utils/Trace.h>
 
 #include <cutils/log.h>
 #include <sync/sync.h>
@@ -174,6 +176,7 @@
 }
 
 int DrmCompositor::Composite() {
+  ATRACE_CALL();
   int ret = pthread_mutex_lock(&lock_);
   if (ret) {
     ALOGE("Failed to acquire compositor lock %d", ret);