title: Start activity with flag FLAG_ACTIVITY_NEW_TASK, the new activity didn't in new task
body: <p>First I start <code>Activity</code> with <code>FLAG_ACTIVITY_NEW_TASK</code>,then using command 'adb shell dumpsys <code>Activity</code>',finally i find the two activities in one task。  </p>
  
  <pre><code> Intent intent = new Intent(this, Main2Activity.class);
   intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
   startActivity(intent);
  </code></pre>
  
  <p>These <code>Activity</code> were normal, i didn't modify them。These were stack information.</p>
  
  <pre><code>ACTIVITY MANAGER ACTIVITIES (dumpsys activity activities)
  Display #0 (activities from top to bottom):
    Stack #1:
    mFullscreen=true
    mBounds=null
      Task id #2493
      mFullscreen=true
      mBounds=null
      mMinWidth=-1
      mMinHeight=-1
      mLastNonFullscreenBounds=null
      * TaskRecord{cb64df8 #2493 A=com.example.flag U=0 StackId=1 sz=2}
        userId=0 effectiveUid=u0a63 mCallingUid=2000 mUserSetupComplete=true mCallingPackage=null
        affinity=com.example.flag
        intent={act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.example.flag/.MainActivity}
        realActivity=com.example.flag/.MainActivity
        autoRemoveRecents=false isPersistable=true numFullscreen=2 taskType=0 mTaskToReturnTo=1
        rootWasReset=false mNeverRelinquishIdentity=true mReuseTask=false mLockTaskAuth=LOCK_TASK_AUTH_PINNABLE
        Activities=[ActivityRecord{b786d24 u0 com.example.flag/.MainActivity t2493}, ActivityRecord{afe6f61 u0 com.example.flag/.Main2Activity t2493}]
        askedCompatMode=false inRecents=true isAvailable=true
        lastThumbnail=null lastThumbnailFile=/data/system_ce/0/recent_images/2493_task_thumbnail.png
        stackId=1
        hasBeenVisible=true mResizeMode=RESIZE_MODE_RESIZEABLE isResizeable=true firstActiveTime=1499670460422 lastActiveTime=1499670460422 (inactive for 23s)
        * Hist #1: ActivityRecord{afe6f61 u0 com.example.flag/.Main2Activity t2493}
            packageName=com.example.flag processName=com.example.flag
            launchedFromUid=10063 launchedFromPackage=com.example.flag userId=0
            app=ProcessRecord{b30f2d1 11785:com.example.flag/u0a63}
            Intent { flg=0x10000000 cmp=com.example.flag/.Main2Activity }
            frontOfTask=false task=TaskRecord{cb64df8 #2493 A=com.example.flag U=0 StackId=1 sz=2}
            taskAffinity=com.example.flag
            realActivity=com.example.flag/.Main2Activity
            baseDir=/data/app/com.example.flag-1/base.apk
            dataDir=/data/user/0/com.example.flag
            stateNotNeeded=false componentSpecified=true mActivityType=0
            compat={480dpi} labelRes=0x7f060021 icon=0x7f030000 theme=0x7f0800a3
            config={1.0 460mcc1mnc [zh_CN_#Hans,en_US,zh_TW_#Hant] ldltr sw360dp w360dp h616dp 480dpi nrml long port finger -keyb/v/h -nav/h s.8}
            taskConfigOverride={1.0 ?mcc?mnc ?localeList ?layoutDir ?swdp ?wdp ?hdp ?density ?lsize ?long ?orien ?uimode ?night ?touch ?keyb/?/? ?nav/?}
            taskDescription: iconFilename=null label="null" color=ff3f51b5
            launchFailed=false launchCount=1 lastLaunchTime=-23s446ms
            haveState=false icicle=null
            state=RESUMED stopped=false delayedResume=false finishing=false
            keysPaused=false inHistory=true visible=true sleeping=false idle=true mStartingWindowState=STARTING_WINDOW_NOT_SHOWN
            fullscreen=true noDisplay=false immersive=false launchMode=0
            frozenBeforeDestroy=false forceNewConfig=false
            mActivityType=APPLICATION_ACTIVITY_TYPE
            waitingVisible=false nowVisible=true lastVisibleTime=-22s952ms
            resizeMode=RESIZE_MODE_RESIZEABLE
        * Hist #0: ActivityRecord{b786d24 u0 com.example.flag/.MainActivity t2493}
            packageName=com.example.flag processName=com.example.flag
            launchedFromUid=2000 launchedFromPackage=null userId=0
            app=ProcessRecord{b30f2d1 11785:com.example.flag/u0a63}
            Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10000000 cmp=com.example.flag/.MainActivity }
            frontOfTask=true task=TaskRecord{cb64df8 #2493 A=com.example.flag U=0 StackId=1 sz=2}
            taskAffinity=com.example.flag
            realActivity=com.example.flag/.MainActivity
            baseDir=/data/app/com.example.flag-1/base.apk
            dataDir=/data/user/0/com.example.flag
            stateNotNeeded=false componentSpecified=true mActivityType=0
            compat={480dpi} labelRes=0x7f060021 icon=0x7f030000 theme=0x7f0800a3
            config={1.0 460mcc1mnc [zh_CN_#Hans,en_US,zh_TW_#Hant] ldltr sw360dp w360dp h616dp 480dpi nrml long port finger -keyb/v/h -nav/h s.8}
            taskConfigOverride={1.0 ?mcc?mnc ?localeList ?layoutDir ?swdp ?wdp ?hdp ?density ?lsize ?long ?orien ?uimode ?night ?touch ?keyb/?/? ?nav/?}
            taskDescription: iconFilename=null label="null" color=ff3f51b5
            launchFailed=false launchCount=0 lastLaunchTime=-57s646ms
            haveState=true icicle=Bundle[mParcelledData.dataSize=604]
            state=STOPPED stopped=true delayedResume=false finishing=false
            keysPaused=false inHistory=true visible=false sleeping=false idle=true mStartingWindowState=STARTING_WINDOW_SHOWN
            fullscreen=true noDisplay=false immersive=false launchMode=0
            frozenBeforeDestroy=false forceNewConfig=false
            mActivityType=APPLICATION_ACTIVITY_TYPE
            waitingVisible=false nowVisible=false lastVisibleTime=-56s921ms
            resizeMode=RESIZE_MODE_RESIZEABLE
  </code></pre>