base: Erase unused FOR_EACH_OBSERVER macro.

We use the range based for loop from now.

BUG=655021

Review-Url: https://codereview.chromium.org/2451933003
Cr-Commit-Position: refs/heads/master@{#427623}

PRESUBMIT.py

@@ -307,15 +307,6 @@
       True,
       (),
     ),
-    (
-      r'FOR_EACH_OBSERVER(',
-      (
-        'Use range-based for loops to iterate through base::ObserverList, e.g.',
-        '        for (auto& observer : observers) { observer.Observe(); }',
-      ),
-      True,
-      (),
-    ),
     (
       r'STLDeleteContainerPointers',  # http://crbug.com/555865
       (

base/android/java/src/org/chromium/base/ObserverList.java

@@ -21,7 +21,7 @@
  * The implementation (and the interface) is heavily influenced by the C++ ObserverList.
  * Notable differences:
  *   - The iterator implements NOTIFY_EXISTING_ONLY.
- *   - The FOR_EACH_OBSERVER closure is left to the clients to implement in terms of iterator().
+ *   - The range-based for loop is left to the clients to implement in terms of iterator().
  * <p/>
  * This class is not threadsafe. Observers MUST be added, removed and will be notified on the same
  * thread this is created.

base/observer_list.h

@@ -344,13 +344,6 @@ class ObserverList : public ObserverListBase<ObserverType> {
   }
 };
 
-// Deprecated. Use the range-based for loop instead.
-#define FOR_EACH_OBSERVER(ObserverType, observer_list, func) \
-  do {                                                       \
-    for (ObserverType & o : observer_list)                   \
-      o.func;                                                \
-  } while (0)
-
 }  // namespace base
 
 #endif  // BASE_OBSERVER_LIST_H_

base/observer_list_unittest.cc

@@ -606,7 +606,8 @@ TEST(ObserverListTest, IteratorOutlivesList) {
   ListDestructor a(observer_list);
   observer_list->AddObserver(&a);
 
-  FOR_EACH_OBSERVER(Foo, *observer_list, Observe(0));
+  for (auto& observer : *observer_list)
+    observer.Observe(0);
   // If this test fails, there'll be Valgrind errors when this function goes out
   // of scope.
 }