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

tests/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 "Test.h"
 
 #include "SkCommandLineFlags.h"
@@ skipping 18 matching lines @@
         }
     }
     result.append(this->condition);
     return result;
 }
 
 SkString skiatest::GetTmpDir() {
     const char* tmpDir = FLAGS_tmpDir.isEmpty() ? nullptr : FLAGS_tmpDir[0];
     return SkString(tmpDir);
 }
+
+skiatest::Timer::Timer() : fStartNanos(SkTime::GetNSecs()) {}
+
+double skiatest::Timer::elapsedNs() const {
+    return SkTime::GetNSecs() - fStartNanos;
+}
+
+double skiatest::Timer::elapsedMs() const { return this->elapsedNs() * 1e-6; }
+
+SkMSec skiatest::Timer::elapsedMsInt() const {
+    const double elapsedMs = this->elapsedMs();
+    SkASSERT(SK_MSecMax >= elapsedMs);
+    return static_cast<SkMSec>(elapsedMs);
+}