hindsight: add some safeguards.

If for some reason, lots of actions are generated at very short period
of time, we need to make sure:

(1) We don't use too much memory.
(2) We don't use too much disk.

Bug: 1012936
Change-Id: I00e9d79c3a45dc3bdbe682bc2e9aae532bc00862
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1866091Reviewed-by: Tony Yeoman <tby@chromium.org>
Reviewed-by: Charles . <charleszhao@chromium.org>
Commit-Queue: Charles . <charleszhao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706766}

chrome/browser/ui/app_list/search/cros_action_history/cros_action_recorder.cc

@@ -21,6 +21,12 @@ namespace app_list {
 namespace {
 
 constexpr int kSecondsPerDay = 86400;
+// If |CrOSActionRecorder::actions_| gets longer than this, force a Flush to
+// disk.
+constexpr int kActionLimitInMemory = 3600;
+// If current file already contains more record than this, skip the rest for
+// that day.
+constexpr int kActionLimitPerFile = 100000;
 
 enum CrOSActionRecorderType {
   kDefault = 0,
@@ -39,6 +45,9 @@ void SaveToDiskOnWorkerThread(const CrOSActionHistoryProto actions,
   if (!actions_to_write.ParseFromString(proto_str))
     actions_to_write.Clear();
 
+  if (actions_to_write.actions_size() > kActionLimitPerFile)
+    return;
+
   actions_to_write.MergeFrom(actions);
   const std::string proto_str_to_write = actions_to_write.SerializeAsString();
 
@@ -112,8 +121,12 @@ void CrOSActionRecorder::RecordAction(
 
 void CrOSActionRecorder::MaybeFlushToDisk() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  if (actions_.actions().empty())
+    return;
+
   const base::Time now = base::Time::Now();
-  if (now - last_save_timestamp_ >= kSaveInternal) {
+  if (now - last_save_timestamp_ >= kSaveInternal ||
+      actions_.actions_size() > kActionLimitInMemory) {
     last_save_timestamp_ = now;
 
     // Writes the predictor proto to disk asynchronously.