Change SkTime::GetMSecs to double; ensure values stored in SkMSec do not overflow.

tests/skia_test.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "CrashHandler.h"
 #include "OverwriteLine.h"
 #include "Resources.h"
@@ skipping 77 matching lines @@
           }
           bool verbose() const override { return FLAGS_veryVerbose; }
           void reportFailed(const skiatest::Failure& failure) override {
               SkDebugf("\nFAILED: %s", failure.toString().c_str());
               fError = true;
           }
           bool fError;
           int fTestCount;
       } reporter;
 
-      const SkMSec start = SkTime::GetMSecs();
+      const Timer timer;
       fTest.proc(&reporter, fGrContextFactory);
-      SkMSec elapsed = SkTime::GetMSecs() - start;
+      SkMSec elapsed = timer.elapsedMsInt();
       if (reporter.fError) {
           fStatus->reportFailure();
       }
       fStatus->endTest(fTest.name, !reporter.fError, elapsed,
                        reporter.fTestCount);
   }
 
 private:
     Test fTest;
     Status* fStatus;
@@ skipping 109 matching lines @@
     SkDebugf("\n");
     return (status.failCount() == 0) ? 0 : 1;
 }
 
 #if !defined(SK_BUILD_FOR_IOS)
 int main(int argc, char** argv) {
     SkCommandLineFlags::Parse(argc, argv);
     return test_main();
 }
 #endif