Clean up a few includes, introduce iwyu.

src/ports/SkTime_Unix.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
-
 #include "SkTime.h"
+#include "SkTypes.h"
 
 #include <sys/time.h>
 #include <time.h>
 
 void SkTime::GetDateTime(DateTime* dt)
 {
     if (dt)
     {
         tzset();  // initialize timezone variable;
         time_t m_time;
@@ skipping 13 matching lines @@
         dt->fSecond     = SkToU8(tstruct->tm_sec);
     }
 }
 
 SkMSec SkTime::GetMSecs()
 {
     struct timeval tv;
     gettimeofday(&tv, NULL);
     return (SkMSec) (tv.tv_sec * 1000 + tv.tv_usec / 1000 ); // microseconds to milliseconds
 }