Disallow adding ContextLifecycleObservers during iteration.

Source/core/core.gypi

Index: Source/core/core.gypi
diff --git a/Source/core/core.gypi b/Source/core/core.gypi
index f92eb36fcce4f2a80e86a798b0021272ab7fd163..8661a8343e2750d3e24fd61c2d9435b62f42f3c7 100644
--- a/Source/core/core.gypi
+++ b/Source/core/core.gypi
@@ -1459,7 +1459,6 @@
             'frame/DOMWindowEventHandlers.h',
             'frame/DOMWindowLifecycleNotifier.cpp',
             'frame/DOMWindowLifecycleNotifier.h',
-            'frame/DOMWindowLifecycleObserver.cpp',
             'frame/DOMWindowLifecycleObserver.h',
             'frame/DOMWindowProperty.cpp',
             'frame/DOMWindowProperty.h',
@@ -1474,7 +1473,6 @@
             'frame/Frame.cpp',
             'frame/Frame.h',
             'frame/FrameConsole.cpp',
-            'frame/FrameDestructionObserver.cpp',
             'frame/FrameDestructionObserver.h',
             'frame/FrameHost.cpp',
             'frame/FrameHost.h',
@@ -1768,7 +1766,6 @@
             'page/PageAnimator.h',
             'page/PageLifecycleNotifier.cpp',
             'page/PageLifecycleNotifier.h',
-            'page/PageLifecycleObserver.cpp',
             'page/PageLifecycleObserver.h',
             'page/PagePopupClient.cpp',
             'page/PagePopupClient.h',
@@ -2107,7 +2104,6 @@
             'dom/ContextFeatures.h',
             'dom/ContextLifecycleNotifier.cpp',
             'dom/ContextLifecycleNotifier.h',
-            'dom/ContextLifecycleObserver.cpp',
             'dom/ContextLifecycleObserver.h',
             'dom/CrossThreadTask.h',
             'dom/DOMArrayBuffer.cpp',
@@ -2167,7 +2163,6 @@
             'dom/DocumentLifecycle.h',
             'dom/DocumentLifecycleNotifier.cpp',
             'dom/DocumentLifecycleNotifier.h',
-            'dom/DocumentLifecycleObserver.cpp',
             'dom/DocumentLifecycleObserver.h',
             'dom/DocumentMarker.cpp',
             'dom/DocumentMarkerController.cpp',