Replace ScopedObservation::RemoveObservation with Reset().

This makes the class simpler to use in the common case.

Bug: 1145565
Change-Id: Ib6aab62eebf4e402e364687d4224d0f8d7077e6a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2549534Reviewed-by: François Doray <fdoray@chromium.org>
Commit-Queue: Sigurður Ásgeirsson <siggi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#830231}

base/scoped_observation.h

@@ -51,10 +51,7 @@ class ScopedObservation {
   explicit ScopedObservation(Observer* observer) : observer_(observer) {}
   ScopedObservation(const ScopedObservation&) = delete;
   ScopedObservation& operator=(const ScopedObservation&) = delete;
-  ~ScopedObservation() {
-    if (IsObserving())
-      RemoveObservation();
-  }
+  ~ScopedObservation() { Reset(); }
 
   // Adds the object passed to the constructor as an observer on |source|.
   // IsObserving() must be false.
@@ -64,11 +61,11 @@ class ScopedObservation {
     (source_->*AddObsFn)(observer_);
   }
 
-  // Remove the object passed to the constructor as an observer from |source|.
-  void RemoveObservation() {
-    DCHECK_NE(source_, nullptr);
-    (source_->*RemoveObsFn)(observer_);
-    source_ = nullptr;
+  // Remove the object passed to the constructor as an observer from |source_|
+  // if currently observing. Does nothing otherwise.
+  void Reset() {
+    if (IsObserving())
+      RemoveObservation();
   }
 
   // Returns true if any source is being observed.
@@ -80,6 +77,14 @@ class ScopedObservation {
     return source_ == source;
   }
 
+  // Remove the object passed to the constructor as an observer from |source_|.
+  // This method is DEPRECATED, please use Reset().
+  void RemoveObservation() {
+    DCHECK_NE(source_, nullptr);
+    (source_->*RemoveObsFn)(observer_);
+    source_ = nullptr;
+  }
+
  private:
   Observer* const observer_;
 

base/scoped_observation_unittest.cc

@@ -77,6 +77,25 @@ TEST(ScopedObservationTest, RemoveObservation) {
   EXPECT_EQ(0u, s1.num_observers());
 }
 
+TEST(ScopedObservationTest, Reset) {
+  TestSource s1;
+  TestSourceObserver o1;
+  TestScopedObservation obs(&o1);
+  EXPECT_EQ(0u, s1.num_observers());
+  obs.Reset();
+
+  obs.Observe(&s1);
+  EXPECT_EQ(1u, s1.num_observers());
+  EXPECT_TRUE(s1.HasObserver(&o1));
+
+  obs.Reset();
+  EXPECT_EQ(0u, s1.num_observers());
+
+  // Safe to call with no observation.
+  obs.Reset();
+  EXPECT_EQ(0u, s1.num_observers());
+}
+
 TEST(ScopedObservationTest, IsObserving) {
   TestSource s1;
   TestSourceObserver o1;