Put rethrowable first user action in a cancelable Callback

And cancel it on expiration.

Bug: 881907
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: I09af1c34ebf11b51a9cd7d0bb4925d7e97ddc3bb
Reviewed-on: https://chromium-review.googlesource.com/1219611
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590304}

ios/chrome/browser/metrics/first_user_action_recorder.cc

@@ -109,6 +109,10 @@ FirstUserActionRecorder::~FirstUserActionRecorder() {
 
 void FirstUserActionRecorder::Expire() {
   std::string log_message = "Recording 'Expiration' for first user action type";
+  // If there is a pending rethrowable action, it could technically be logged.
+  // But as FirstUserActionRecorder will be destroyed in this runloop, it is too
+  // late.
+  rethrow_callback_.Cancel();
   RecordAction(EXPIRATION, log_message);
 }
 
@@ -183,9 +187,11 @@ bool FirstUserActionRecorder::ShouldProcessAction(
   if (!action_pending_ &&
       ArrayContainsString(kRethrownActions, arraysize(kRethrownActions),
                           action_name.c_str())) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
-        FROM_HERE, base::Bind(&FirstUserActionRecorder::OnUserAction,
-                              base::Unretained(this), action_name));
+    rethrow_callback_.Reset(
+        base::BindOnce(&FirstUserActionRecorder::OnUserAction,
+                       base::Unretained(this), action_name));
+    base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
+                                                  rethrow_callback_.callback());
     action_pending_ = true;
     return false;
   }

ios/chrome/browser/metrics/first_user_action_recorder.h

@@ -7,6 +7,7 @@
 
 #include <vector>
 
+#include "base/cancelable_callback.h"
 #include "base/metrics/user_metrics.h"
 #include "base/time/time.h"
 
@@ -88,6 +89,10 @@ class FirstUserActionRecorder {
   // The callback to invoke when an action is recorded.
   base::ActionCallback action_callback_;
 
+  // A potential action that needs to be confirmed if there is no other relevant
+  // action.
+  base::CancelableOnceClosure rethrow_callback_;
+
   DISALLOW_COPY_AND_ASSIGN(FirstUserActionRecorder);
 };