It appears to me that some other objects owned by LocalFrame should be better owned by DOMWindow:
- Editor
- SpellChecker
- InputMethodController
- IdleSpellCheckCallback

Is there any reason that they are better owned by LocalFrame?

>Is there any reason that they are better owned by LocalFrame?
No, it is historical reason; ease of lifetime management with ref-counting(?) 
Oilpan solves ref-counting issue.

We extend coverage of this issue.

We should transfer ownership of following classes to DOMWindow from LocalFrame
 - FamreSelection; should be renamed to WindowSeleciton
 - Editor
 - SpellChecker; we also move IdleSpellCheckerCallback to SpellChecker, since IdleSpellCheckerCallback is implementation detail
 - InputMethodCOntroller

Since lifetime of these classes is as same as DOMWindow.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d9e6a0b2197094e8fd4b4f4cb66f19bdfd213403

commit d9e6a0b2197094e8fd4b4f4cb66f19bdfd213403
Author: xiaochengh <xiaochengh@chromium.org>
Date: Mon Feb 27 05:20:49 2017

Move ownership of IdleSpellCheckCallback from LocalFrame to SpellChecker

IdleSpellCheckCallback is an implementation detail of Blink's SpellChecker,
and should better be owned by and hidden in SpellChecker, instead of being
exposed from LocalFrame.

This patch hence moves ownership of IdleSpellCheckCallback to SpellChecker.

BUG= 517298 , 695359

Review-Url: https://codereview.chromium.org/2714113003
Cr-Commit-Position: refs/heads/master@{#453157}

[modify] https://crrev.com/d9e6a0b2197094e8fd4b4f4cb66f19bdfd213403/third_party/WebKit/Source/core/editing/spellcheck/IdleSpellCheckCallback.cpp
[modify] https://crrev.com/d9e6a0b2197094e8fd4b4f4cb66f19bdfd213403/third_party/WebKit/Source/core/editing/spellcheck/IdleSpellCheckCallback.h
[modify] https://crrev.com/d9e6a0b2197094e8fd4b4f4cb66f19bdfd213403/third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.cpp
[modify] https://crrev.com/d9e6a0b2197094e8fd4b4f4cb66f19bdfd213403/third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.h
[modify] https://crrev.com/d9e6a0b2197094e8fd4b4f4cb66f19bdfd213403/third_party/WebKit/Source/core/frame/LocalFrame.cpp
[modify] https://crrev.com/d9e6a0b2197094e8fd4b4f4cb66f19bdfd213403/third_party/WebKit/Source/core/frame/LocalFrame.h
[modify] https://crrev.com/d9e6a0b2197094e8fd4b4f4cb66f19bdfd213403/third_party/WebKit/Source/core/testing/Internals.cpp
[modify] https://crrev.com/d9e6a0b2197094e8fd4b4f4cb66f19bdfd213403/third_party/WebKit/Source/web/WebLeakDetector.cpp

We should not move them to Page even if they work on active frame. 
When Page owns them, we need to consider OOPIF[1]


[1] https://codereview.chromium.org/2953503004#msg18

Because of lifetime of DOMWindow is longer than Document, we want to move Editor, etc, to Document. But, some Document doesn't associate to Frame.

We need to think more about lifetime of Editor...

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