Fix random number generation in disk_cache_perftests.

net/disk_cache/disk_cache_perftest.cc

Index: net/disk_cache/disk_cache_perftest.cc
diff --git a/net/disk_cache/disk_cache_perftest.cc b/net/disk_cache/disk_cache_perftest.cc
index daeb6770b91d5fe02c89141c183a8db13aa4aad6..f935780b5fbd5ec9e8583b157d545a8545456082 100644
--- a/net/disk_cache/disk_cache_perftest.cc
+++ b/net/disk_cache/disk_cache_perftest.cc
@@ -11,6 +11,7 @@
 #include "base/files/file_path.h"
 #include "base/hash.h"
 #include "base/process/process_metrics.h"
+#include "base/rand_util.h"
 #include "base/run_loop.h"
 #include "base/strings/string_util.h"
 #include "base/test/perf_time_logger.h"
@@ -114,7 +115,7 @@ bool DiskCachePerfTest::TimeWrite() {
   for (int i = 0; i < kNumEntries; i++) {
     TestEntry entry;
     entry.key = GenerateKey(true);
-    entry.data_len = rand() % kBodySize;
+    entry.data_len = base::RandInt(0, kBodySize);
     entries_.push_back(entry);
 
     disk_cache::Entry* cache_entry;
@@ -196,9 +197,6 @@ bool DiskCachePerfTest::TimeRead(WhatToRead what_to_read,
 }
 
 TEST_F(DiskCachePerfTest, BlockfileHashes) {
-  int seed = static_cast<int>(Time::Now().ToInternalValue());
-  srand(seed);
-
   base::PerfTimeLogger timer("Hash disk cache keys");
   for (int i = 0; i < 300000; i++) {
     std::string key = GenerateKey(true);
@@ -270,7 +268,7 @@ TEST_F(DiskCachePerfTest, SimpleCacheBackendPerformance) {
 
 int BlockSize() {
   // We can use form 1 to 4 blocks.

[jkarlin, 2016/11/15 12:18:29]

While you're here..
s/form/from/

[gavinp, 2016/11/15 15:30:53]

Done. Also removed the function; documented the role with a variable instead.
And killed the comment rather than fixing it, since it was just recapitulating
code.

-  return (rand() & 0x3) + 1;
+  return base::RandInt(1, 4);
 }
 
 // Creating and deleting "entries" on a block-file is something quite frequent
@@ -284,9 +282,6 @@ TEST_F(DiskCachePerfTest, BlockFilesPerformance) {
   disk_cache::BlockFiles files(cache_path_);
   ASSERT_TRUE(files.Init(true));
 
-  int seed = static_cast<int>(Time::Now().ToInternalValue());
-  srand(seed);
-
   const int kNumBlocks = 60000;
   disk_cache::Addr address[kNumBlocks];
 
@@ -302,7 +297,8 @@ TEST_F(DiskCachePerfTest, BlockFilesPerformance) {
   base::PerfTimeLogger timer2("Create and delete blocks");
 
   for (int i = 0; i < 200000; i++) {
-    int entry = rand() * (kNumBlocks / RAND_MAX + 1);
+    int entry = base::RandInt(0, kNumBlocks);

[jkarlin, 2016/11/15 12:18:29]

base::RandInt(0, kNumBlocks-1) since it's inclusive and this value is used as an
index. Then you can drop the condition below.

[gavinp, 2016/11/15 15:30:54]

Done.

I can't believe these gymnastics. This is such a horrible test.

+
     if (entry >= kNumBlocks)

[jkarlin, 2016/11/15 12:18:29]

This condition should go.

[gavinp, 2016/11/15 15:30:54]

Done.

       entry = 0;