[chromium] Expose setSelectionIncludesAltImageText in WebSettings
https://bugs.webkit.org/show_bug.cgi?id=113316

Reviewed by Dimitri Glazkov.

Enabling this setting allows plain text clipboard content to include alt
text like on Firefox and IE10.

* public/WebSettings.h:
(WebSettings):
* src/WebSettingsImpl.cpp:
(WebKit::WebSettingsImpl::setSelectionIncludesAltImageText):
* src/WebSettingsImpl.h:
(WebSettingsImpl):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146917 268f45cc-cd09-0410-ab3c-d52691b4dbfc