[Soft fetches] Set-up different intervals for <Chrome started> events.

components/ntp_snippets/pref_names.h

Index: components/ntp_snippets/pref_names.h
diff --git a/components/ntp_snippets/pref_names.h b/components/ntp_snippets/pref_names.h
index 9826eb9e9cab9403d0c73cf79e3080b0370bc27c..ef1595a9aefaf3b80678d75d89a24bccaca14f6e 100644
--- a/components/ntp_snippets/pref_names.h
+++ b/components/ntp_snippets/pref_names.h
@@ -18,22 +18,25 @@ extern const char kRemoteSuggestionCategories[];
 
 // The pref name for the last time when a background fetch was attempted.
 extern const char kSnippetLastFetchAttempt[];
-// The pref name for the currently applied minimal interval between two
-// successive soft background fetches that react to user activity (such as
-// opening Chrome) when there is a WiFi connectivity.
-extern const char kSnippetSoftFetchingIntervalWifi[];
-// The pref name for the currently applied minimal interval between two
-// successive soft background fetches that react to user activity (such as
-// opening Chrome) when there is no WiFi connectivity.
-extern const char kSnippetSoftFetchingIntervalFallback[];
-
-// The pref name for the currently-scheduled background fetching interval when
-// there is WiFi connectivity.
+
+////////////////// Minimal interval between two successive background fetches.
+// The pref names for for the currently applied minimal intervals. For each
+// trigger there are two intervals stored in prefs:
+//  - "Wifi" for situations with unmetered network connectivity, and

[markusheintz_, 2017/05/15 09:35:47]

We don't know whether a WIFI is unmetered.

[jkrcal, 2017/05/15 11:40:24]

Expanded to explain better.

+//  - "Fallback" for situations with only metered network.

[markusheintz_, 2017/05/15 09:35:47]

Same here just the other way around.

[jkrcal, 2017/05/15 11:40:24]

ditto

+
+// Trigger: wake-up of the persistent scheduler.

[markusheintz_, 2017/05/15 09:35:47]

The trigger comments are confusing. What information do you want to convey here?

That logic for checking whether this interval has already elapsed are triggered
by the mention situation?

[jkrcal, 2017/05/15 11:40:24]

ditto

 extern const char kSnippetPersistentFetchingIntervalWifi[];
-// The pref name for the currently-scheduled background fetching interval when
-// there is no WiFi connectivity.
 extern const char kSnippetPersistentFetchingIntervalFallback[];
 
+// Trigger: browser started-up (both cold and warm start).
+extern const char kSnippetStartupFetchingIntervalWifi[];
+extern const char kSnippetStartupFetchingIntervalFallback[];
+
+// Trigger: suggestions shown to the user.
+extern const char kSnippetShownFetchingIntervalWifi[];
+extern const char kSnippetShownFetchingIntervalFallback[];
+
 // The pref name for today's count of RemoteSuggestionsFetcher requests, so far.
 extern const char kSnippetFetcherRequestCount[];
 // The pref name for today's count of RemoteSuggestionsFetcher interactive