Track when profiles are last used.

chrome/browser/profiles/profile_info_cache.cc

Index: chrome/browser/profiles/profile_info_cache.cc
diff --git a/chrome/browser/profiles/profile_info_cache.cc b/chrome/browser/profiles/profile_info_cache.cc
index 6aeedf0f99b10a44e9b24848bd342f33384aa1b4..e1bd4ae2cad80240fa1caff340c0a4a0ebf46e10 100644
--- a/chrome/browser/profiles/profile_info_cache.cc
+++ b/chrome/browser/profiles/profile_info_cache.cc
@@ -53,6 +53,7 @@ const char kIsManagedKey[] = "is_managed";
 const char kSigninRequiredKey[] = "signin_required";
 const char kManagedUserId[] = "managed_user_id";
 const char kProfileIsEphemeral[] = "is_ephemeral";
+const char kActiveTimeKey[] = "active_time";
 
 const char kDefaultUrlPrefix[] = "chrome://theme/IDR_PROFILE_AVATAR_";
 const char kGAIAPictureFileName[] = "Google Profile Picture.png";
@@ -309,6 +310,15 @@ base::FilePath ProfileInfoCache::GetPathOfProfileAtIndex(size_t index) const {
   return user_data_dir_.AppendASCII(sorted_keys_[index]);
 }
 
+base::Time ProfileInfoCache::GetProfileActive(size_t index) const {
+  double dt;
+  if (GetInfoForProfileAtIndex(index)->GetDouble(kActiveTimeKey, &dt)) {
+    return base::Time::FromDoubleT(dt);
+  } else {
+    return base::Time();
+  }
+}
+
 base::string16 ProfileInfoCache::GetUserNameOfProfileAtIndex(
     size_t index) const {
   base::string16 user_name;
@@ -474,6 +484,14 @@ size_t ProfileInfoCache::GetAvatarIconIndexOfProfileAtIndex(size_t index)
   return icon_index;
 }
 
+void ProfileInfoCache::SetProfileActive(size_t index) {
+  scoped_ptr<base::DictionaryValue> info(
+      GetInfoForProfileAtIndex(index)->DeepCopy());
+  info->SetDouble(kActiveTimeKey, base::Time::Now().ToDoubleT());
+  // This takes ownership of |info|.
+  SetInfoForProfileAtIndex(index, info.release());
+}
+
 void ProfileInfoCache::SetNameOfProfileAtIndex(size_t index,
                                                const base::string16& name) {
   scoped_ptr<base::DictionaryValue> info(