[net] Set default HostCache size according to HostCacheSize field trial.

net/base/host_cache.cc

Index: net/base/host_cache.cc
diff --git a/net/base/host_cache.cc b/net/base/host_cache.cc
index 5221fca9caeae744ad36b4b477f24afd0592dee4..be674888e278897b62e47490ac3dfd315ad7a307 100644
--- a/net/base/host_cache.cc
+++ b/net/base/host_cache.cc
@@ -5,6 +5,8 @@
 #include "net/base/host_cache.h"
 
 #include "base/logging.h"
+#include "base/metrics/field_trial.h"
+#include "base/string_number_conversions.h"
 #include "net/base/net_errors.h"
 
 namespace net {
@@ -84,11 +86,16 @@ scoped_ptr<HostCache> HostCache::CreateDefaultCache() {
   // Increase HostCache size for the duration of the async DNS field trial.
   // http://crbug.com/143454
   // TODO(szym): Determine the best size. http://crbug.com/114277
-  static const size_t kMaxHostCacheEntries = 1000;
+  size_t max_entries = 1000;
 #else
-  static const size_t kMaxHostCacheEntries = 100;
+  const size_t kSaneMaxEntries = 1 << 20;
+  size_t max_entries = 0;
+  if (!base::StringToSizeT(base::FieldTrialList::FindFullName("HostCacheSize"),
+                           &max_entries) || max_entries > kSaneMaxEntries) {

[mmenke, 2012/11/07 16:11:00]

How are we going to handle recording histograms on ChromeOS?  Not set the
HostCacheSize via Finch, not set it Chrome side, not record HostCacheSize field
trial stats on ChromeOS, just just know enough to ignore them on ChromeOS?

If we're just not going to set it via Finch, then we may want to have this code
run on ChromeOS as well (And default to 1000 entries instead of 100).

[szym, 2012/11/07 16:22:42]

My bad, I forgot to remove the #ifdef. There's no need for breakout on CrOS.
Fixed.

+    max_entries = 100;
+  }
 #endif
-  return make_scoped_ptr(new HostCache(kMaxHostCacheEntries));
+  return make_scoped_ptr(new HostCache(max_entries));
 }
 
 }  // namespace net