Represent speed in GCTracer functions as double instead of int.

test/unittests/heap/scavenge-job-unittest.cc

 // Copyright 2014 the V8 project 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 <limits>
 
 #include "src/globals.h"
 #include "src/heap/scavenge-job.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 53 matching lines @@
 TEST(ScavengeJob, AllocationLimitHighScavengeSpeed) {
   size_t scavenge_speed = kNewSpaceCapacity;
   size_t expected_size =
       static_cast<size_t>(
           kNewSpaceCapacity *
           ScavengeJob::kMaxAllocationLimitAsFractionOfNewSpace) -
       ScavengeJob::kBytesAllocatedBeforeNextIdleTask;
   EXPECT_FALSE(ScavengeJob::ReachedIdleAllocationLimit(
       scavenge_speed, expected_size - 1, kNewSpaceCapacity));
   EXPECT_TRUE(ScavengeJob::ReachedIdleAllocationLimit(
-      scavenge_speed, expected_size, kNewSpaceCapacity));
+      scavenge_speed, expected_size + 1, kNewSpaceCapacity));
 }
 
 
 TEST(ScavengeJob, EnoughIdleTimeForScavengeUnknownScavengeSpeed) {
   size_t scavenge_speed = ScavengeJob::kInitialScavengeSpeedInBytesPerMs;
   size_t new_space_size = 1 * MB;
   size_t expected_time = (new_space_size + scavenge_speed - 1) / scavenge_speed;
   EXPECT_TRUE(
       ScavengeJob::EnoughIdleTimeForScavenge(expected_time, 0, new_space_size));
   EXPECT_FALSE(ScavengeJob::EnoughIdleTimeForScavenge(expected_time - 1, 0,
@@ skipping 17 matching lines @@
   size_t new_space_size = 1 * MB;
   size_t expected_time = (new_space_size + scavenge_speed - 1) / scavenge_speed;
   EXPECT_TRUE(ScavengeJob::EnoughIdleTimeForScavenge(
       expected_time, scavenge_speed, new_space_size));
   EXPECT_FALSE(ScavengeJob::EnoughIdleTimeForScavenge(
       expected_time - 1, scavenge_speed, new_space_size));
 }
 
 }  // namespace internal
 }  // namespace v8