[Merge to 2883] Fix memory leaks in macOS Sierra for IME.

[Merge to 2883] Fix memory leaks in macOS Sierra for IME.

> The documentation for NSTextInputClient states that:
>   -selectedRange should return { NSNotFound, 0 } if there is no selection range.
>   -attributedSubstringForProposedRange:actualRange: must be able to handle
>   invalid ranges.
>
> The previous implementations in RenderWidgetHostViewCocoa failed to do either,
> which results in catastrophic memory leaks on macOS Sierra during IME. In an
> ASAN build, AppKit attempts to allocate ~2^64 bytes of memory.
>
> BUG=654695
>
> Review-Url: https://codereview.chromium.org/2480893002
> Cr-Commit-Position: refs/heads/master@{#430116}
> (cherry picked from commit 7d85f23cb0235db06b0b6c2de1dc29ae5eaeb8f5)

Committed: https://chromium.googlesource.com/chromium/src/+/da364879b2e82d42525cb8942c652c2403d43ffb

[erikchen, 2016-11-07 18:23:15]

Description was changed from

==========
[Merge to 2883] Fix memory leaks in macOS Sierra for IME.

> The documentation for NSTextInputClient states that:
>   -selectedRange should return { NSNotFound, 0 } if there is no selection
range.
>   -attributedSubstringForProposedRange:actualRange: must be able to handle
>   invalid ranges.
>
> The previous implementations in RenderWidgetHostViewCocoa failed to do either,
> which results in catastrophic memory leaks on macOS Sierra during IME. In an
> ASAN build, AppKit attempts to allocate ~2^64 bytes of memory.
>
> BUG=654695
>
> Review-Url: https://codereview.chromium.org/2480893002
> Cr-Commit-Position: refs/heads/master@{#430116}
> (cherry picked from commit 7d85f23cb0235db06b0b6c2de1dc29ae5eaeb8f5)
==========

to

==========
[Merge to 2883] Fix memory leaks in macOS Sierra for IME.

> The documentation for NSTextInputClient states that:
>   -selectedRange should return { NSNotFound, 0 } if there is no selection
range.
>   -attributedSubstringForProposedRange:actualRange: must be able to handle
>   invalid ranges.
>
> The previous implementations in RenderWidgetHostViewCocoa failed to do either,
> which results in catastrophic memory leaks on macOS Sierra during IME. In an
> ASAN build, AppKit attempts to allocate ~2^64 bytes of memory.
>
> BUG=654695
>
> Review-Url: https://codereview.chromium.org/2480893002
> Cr-Commit-Position: refs/heads/master@{#430116}
> (cherry picked from commit 7d85f23cb0235db06b0b6c2de1dc29ae5eaeb8f5)

Committed:
https://chromium.googlesource.com/chromium/src/+/da364879b2e82d42525cb8942c65...
==========

[erikchen, 2016-11-07 18:23:16]

Committed patchset #1 (id:1) manually as
da364879b2e82d42525cb8942c652c2403d43ffb.