Add Desktop iOS promotion logging to chrome ios app.

ios/chrome/browser/desktop_promotion/desktop_promotion_sync_observer.mm

Index: ios/chrome/browser/desktop_promotion/desktop_promotion_sync_observer.mm
diff --git a/ios/chrome/browser/desktop_promotion/desktop_promotion_sync_observer.mm b/ios/chrome/browser/desktop_promotion/desktop_promotion_sync_observer.mm
new file mode 100644
index 0000000000000000000000000000000000000000..1a9627185a64565eef4e0d4ee2bd5a3e6f28040f
--- /dev/null
+++ b/ios/chrome/browser/desktop_promotion/desktop_promotion_sync_observer.mm
@@ -0,0 +1,85 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "ios/chrome/browser/desktop_promotion/desktop_promotion_sync_observer.h"
+
+#include <memory>
+
+#include "base/metrics/histogram_macros.h"
+#include "base/strings/stringprintf.h"
+#include "base/time/time.h"
+#include "components/browser_sync/profile_sync_service.h"
+#include "components/prefs/pref_service.h"
+#include "ios/chrome/browser/desktop_promotion/histogram_macros.h"
+#include "ios/chrome/browser/pref_names.h"
+
+namespace {
+
+const char* kDesktopIOSPromotionEntrypointHistogramPrefix[] = {

[Mark P, 2017/01/26 23:47:24]

Please put a warning here, as discussed.

[mrefaat, 2017/01/27 18:29:42]

Done.

+    "SavePasswordsNewBubble", "BookmarksNewBubble", "BookmarksExistingBubble",
+    "HistoryPage",
+};
+}
+
+DesktopPromotionSyncObserver::DesktopPromotionSyncObserver(
+    PrefService* pref_service,
+    browser_sync::ProfileSyncService* sync_service)
+    : pref_service_(pref_service), sync_service_(sync_service) {
+  DCHECK(pref_service_);
+  DCHECK(sync_service_);
+  sync_service_->AddObserver(this);
+}
+
+DesktopPromotionSyncObserver::~DesktopPromotionSyncObserver() {
+  sync_service_->RemoveObserver(this);
+}
+
+void DesktopPromotionSyncObserver::OnStateChanged() {
+  if (desktop_metrics_logger_initiated_ ||
+      !sync_service_->GetActiveDataTypes().Has(syncer::PRIORITY_PREFERENCES)) {
+    return;
+  }
+
+  desktop_metrics_logger_initiated_ = true;
+  bool done_logging =
+      pref_service_->GetBoolean(prefs::kDesktopIOSPromotionDone);
+  double last_impression =
+      pref_service_->GetDouble(prefs::kDesktopIOSPromotionLastImpression);
+  base::TimeDelta delta =
+      base::Time::Now() - base::Time::FromDoubleT(last_impression);
+  if (done_logging || delta.InDays() >= 7) {
+    return;
+  }
+
+  // This user have seen the promotion in the last 7 days so it may be a
+  // reason of the installation.
+  int sms_entrypoint =
+      pref_service_->GetInteger(prefs::kDesktopIOSPromotionSMSEntryPoint);
+  int shown_entrypoints =
+      pref_service_->GetInteger(prefs::kDesktopIOSPromotionShownEntryPoints);
+
+  // Entry points are represented on the preference by integers [1..4].
+  // TODO(681885): Add reference to the Entry point Constants defined in the

[Mark P, 2017/01/26 23:47:24]

fwiw, I don't think I've ever see TODO with bug numbers in them.  Is this
standard practice in the iOS code?

[mrefaat, 2017/01/27 18:29:42]

i should have done it crbut.com/bug number 
i was told about this practice in comments when i was contributing to the
desktop code. 

+  // desktop code side.
+  int entrypoint_prefixes_count =
+      arraysize(kDesktopIOSPromotionEntrypointHistogramPrefix);
+  for (int i = 1; i < entrypoint_prefixes_count + 1; i++) {
+    if (sms_entrypoint == i) {
+      UMA_HISTOGRAM_ENUMERATION("DesktopIOSPromotion.SMSSent.IOSSigninReason",
+                                i, entrypoint_prefixes_count + 1);
+      UMA_HISTOGRAM_COUNT_1000_NO_CACHE(

[Mark P, 2017/01/26 23:47:24]

A new header file to define a series of three macros for something used in only
one place seems odd to me.  Why can't you put the actual code here?  Are you
planning to reuse the macros elsewhere?

[mrefaat, 2017/01/27 18:29:42]

removed it.

+          base::StringPrintf(
+              "DesktopIOSPromotion.%s.CompletionTime",
+              kDesktopIOSPromotionEntrypointHistogramPrefix[i - 1]),
+          MAX(0, delta.InHours()));

[Mark P, 2017/01/27 17:35:01]

BTW, where are you getting MAX from?  I normally see code that calls std::max().
 I wonder what this one is doing.

[mrefaat, 2017/01/27 18:29:42]

replaced by std:max - MAX is predifned in Foundation library but i think its
better to use std:max

+    } else {
+      // If the user saw this promotion type, log that it could be a reason
+      // for the signin.
+      if ((1 << i) & shown_entrypoints)
+        UMA_HISTOGRAM_ENUMERATION("DesktopIOSPromotion.NoSMS.IOSSigninReason",
+                                  i, entrypoint_prefixes_count + 1);
+    }
+  }
+  pref_service_->SetBoolean(prefs::kDesktopIOSPromotionDone, true);
+}