Fix off-by-one in fps_meter, fix unit test to catch this.

chrome/browser/android/vr_shell/fps_meter_unittest.cc

 // Copyright 2017 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 "chrome/browser/android/vr_shell/fps_meter.h"
 
 #include "base/macros.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace vr_shell {
@@ skipping 31 matching lines @@
   EXPECT_FALSE(meter.CanComputeFPS());
   EXPECT_FLOAT_EQ(0.0, meter.GetFPS());
 
   base::TimeTicks now = usToTicks(1);
   base::TimeDelta frame_time = usToDelta(16666);
 
   meter.AddFrame(now);
   EXPECT_FALSE(meter.CanComputeFPS());
   EXPECT_FLOAT_EQ(0.0, meter.GetFPS());
 
-  for (int i = 0; i < 5; ++i) {
+  for (size_t i = 0; i < 2 * meter.GetNumFrameTimes(); ++i) {
     now += frame_time;
     meter.AddFrame(now);
     EXPECT_TRUE(meter.CanComputeFPS());
     EXPECT_NEAR(60.0, meter.GetFPS(), kTolerance);
   }
 }
 
 TEST(FPSMeter, AccurateFPSWithHigherFramerate) {
   FPSMeter meter;
   EXPECT_FALSE(meter.CanComputeFPS());
   EXPECT_FLOAT_EQ(0.0, meter.GetFPS());
 
   base::TimeTicks now = usToTicks(1);
   base::TimeDelta frame_time = base::TimeDelta::FromSecondsD(1.0 / 90.0);
 
   meter.AddFrame(now);
   EXPECT_FALSE(meter.CanComputeFPS());
   EXPECT_FLOAT_EQ(0.0, meter.GetFPS());
 
   for (int i = 0; i < 5; ++i) {
     now += frame_time;
     meter.AddFrame(now);
     EXPECT_TRUE(meter.CanComputeFPS());
     EXPECT_NEAR(1.0 / frame_time.InSecondsF(), meter.GetFPS(), kTolerance);
   }
 }
 
 }  // namespace vr_shell