clang/win: Fix a Wenum-compare warning and a few Wwritable-strings warnings.

base/time/time_win_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <windows.h>
 #include <mmsystem.h>
 #include <process.h>
 
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
@@ skipping 160 matching lines @@
   // Note:  This is a somewhat arbitrary test.
   const int kLoops = 10000;
   // Due to the fact that these run on bbots, which are horribly slow,
   // we can't really make any guarantees about minimum runtime.
   // Really, we want these to finish in ~10ms, and that is generous.
   const int kMaxTime = 35;  // Maximum acceptible milliseconds for test.
 
   typedef TimeTicks (*TestFunc)();
   struct TestCase {
     TestFunc func;
-    char *description;
+    const char *description;
   };
   // Cheating a bit here:  assumes sizeof(TimeTicks) == sizeof(Time)
   // in order to create a single test case list.
   COMPILE_ASSERT(sizeof(TimeTicks) == sizeof(Time),
                  test_only_works_with_same_sizes);
   TestCase cases[] = {
     { reinterpret_cast<TestFunc>(Time::Now), "Time::Now" },
     { TimeTicks::Now, "TimeTicks::Now" },
     { TimeTicks::HighResNow, "TimeTicks::HighResNow" },
     { NULL, "" }
@@ skipping 41 matching lines @@
     total_drift += drift_microseconds;
   }
 
   // Sanity check. We expect some time drift to occur, especially across
   // the number of iterations we do.
   EXPECT_LT(0, total_drift);
 
   printf("average time drift in microseconds: %lld\n",
          total_drift / kIterations);
 }