[PrefService] Add GetTimeDelta() and SetTimeDelta() convenience methods.

While not as common of a pattern as storing base::Time in Prefs, it
does show up in a few places, and is the logical continuation of the
Set/GetTime() methods that we currently have.

Change-Id: Ib38c2f4b431733bc4f40323756ea5fc6f68dfbed
Reviewed-on: https://chromium-review.googlesource.com/1103147
Commit-Queue: Sky Malice <skym@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568089}

components/prefs/pref_registry_simple.cc

@@ -91,3 +91,9 @@ void PrefRegistrySimple::RegisterTimePref(const std::string& path,
   RegisterInt64Pref(
       path, default_value.ToDeltaSinceWindowsEpoch().InMicroseconds(), flags);
 }
+
+void PrefRegistrySimple::RegisterTimeDeltaPref(const std::string& path,
+                                               base::TimeDelta default_value,
+                                               uint32_t flags) {
+  RegisterInt64Pref(path, default_value.InMicroseconds(), flags);
+}

components/prefs/pref_registry_simple.h

@@ -75,6 +75,10 @@ class COMPONENTS_PREFS_EXPORT PrefRegistrySimple : public PrefRegistry {
                         base::Time default_value,
                         uint32_t flags = NO_REGISTRATION_FLAGS);
 
+  void RegisterTimeDeltaPref(const std::string& path,
+                             base::TimeDelta default_value,
+                             uint32_t flags = NO_REGISTRATION_FLAGS);
+
  protected:
   ~PrefRegistrySimple() override;
 

components/prefs/pref_service.cc

@@ -480,6 +480,14 @@ base::Time PrefService::GetTime(const std::string& path) const {
       base::TimeDelta::FromMicroseconds(GetInt64(path)));
 }
 
+void PrefService::SetTimeDelta(const std::string& path, base::TimeDelta value) {
+  SetInt64(path, value.InMicroseconds());
+}
+
+base::TimeDelta PrefService::GetTimeDelta(const std::string& path) const {
+  return base::TimeDelta::FromMicroseconds(GetInt64(path));
+}
+
 base::Value* PrefService::GetMutableUserPref(const std::string& path,
                                              base::Value::Type type) {
   CHECK(type == base::Value::Type::DICTIONARY ||

components/prefs/pref_service.h

@@ -16,6 +16,7 @@
 #include <memory>
 #include <set>
 #include <string>
+#include <vector>
 
 #include "base/callback.h"
 #include "base/compiler_specific.h"
@@ -247,11 +248,14 @@ class COMPONENTS_PREFS_EXPORT PrefService {
   uint64_t GetUint64(const std::string& path) const;
 
   // Time helper methods that actually store the given value as a string, which
-  // represents the number of microseconds elapsed since the Windows epoch. Note
-  // that if obtaining the named value via GetDictionary or GetList, the Value
-  // type will be Type::STRING.
+  // represents the number of microseconds elapsed (absolute for TimeDelta and
+  // relative to Windows epoch for Time variants). Note that if obtaining the
+  // named value via GetDictionary or GetList, the Value type will be
+  // Type::STRING.
   void SetTime(const std::string& path, base::Time value);
   base::Time GetTime(const std::string& path) const;
+  void SetTimeDelta(const std::string& path, base::TimeDelta value);
+  base::TimeDelta GetTimeDelta(const std::string& path) const;
 
   // Returns the value of the given preference, from the user pref store. If
   // the preference is not set in the user pref store, returns NULL.

components/prefs/pref_service_unittest.cc

@@ -259,6 +259,35 @@ TEST(PrefServiceTest, SetTimeValue_NullTime) {
   EXPECT_TRUE(prefs.GetTime(kPrefName).is_null());
 }
 
+TEST(PrefServiceTest, SetTimeDeltaValue_RegularTimeDelta) {
+  TestingPrefServiceSimple prefs;
+
+  // Register a zero time delta as the default.
+  prefs.registry()->RegisterTimeDeltaPref(kPrefName, base::TimeDelta());
+  EXPECT_TRUE(prefs.GetTimeDelta(kPrefName).is_zero());
+
+  // Set a time delta and make sure that we can read it without any loss of
+  // precision.
+  const base::TimeDelta delta = base::Time::Now() - base::Time();
+  prefs.SetTimeDelta(kPrefName, delta);
+  EXPECT_EQ(delta, prefs.GetTimeDelta(kPrefName));
+}
+
+TEST(PrefServiceTest, SetTimeDeltaValue_ZeroTimeDelta) {
+  TestingPrefServiceSimple prefs;
+
+  // Register a non-zero time delta as the default.
+  const base::TimeDelta default_delta =
+      base::TimeDelta::FromMicroseconds(12345);
+  prefs.registry()->RegisterTimeDeltaPref(kPrefName, default_delta);
+  EXPECT_FALSE(prefs.GetTimeDelta(kPrefName).is_zero());
+
+  // Set a zero time delta and make sure that it remains zero upon
+  // deserialization.
+  prefs.SetTimeDelta(kPrefName, base::TimeDelta());
+  EXPECT_TRUE(prefs.GetTimeDelta(kPrefName).is_zero());
+}
+
 // A PrefStore which just stores the last write flags that were used to write
 // values to it.
 class WriteFlagChecker : public TestingPrefStore {