[Rlog19] ResearchLog remove unnecessary logSegment{start,end}

Change-Id: I73b7765c764e5f1035f1c37df45345f26aa5acb1

java/src/com/android/inputmethod/research/LogBuffer.java

@@ -110,4 +110,8 @@ public class LogBuffer {
         }
         return logUnit;
     }
+
+    public boolean isEmpty() {
+        return mLogUnits.isEmpty();
+    }
 }

java/src/com/android/inputmethod/research/ResearchLogger.java

@@ -701,6 +701,7 @@ public class ResearchLogger implements SharedPreferences.OnSharedPreferenceChang
     /* package for test */ void publishLogBuffer(final LogBuffer logBuffer,
             final ResearchLog researchLog, final boolean isIncludingPrivateData) {
         final LogUnit openingLogUnit = new LogUnit();
+        if (logBuffer.isEmpty()) return;
         openingLogUnit.addLogStatement(LOGSTATEMENT_LOG_SEGMENT_OPENING, SystemClock.uptimeMillis(),
                 isIncludingPrivateData);
         researchLog.publish(openingLogUnit, true /* isIncludingPrivateData */);