<rdar://problem/7595685>
https://bugs.webkit.org/show_bug.cgi?id=34609

Reviewed by Oliver Hunt.

WebCore: 

Test: editing/pasteboard/drop-inputtext-acquires-style.html

The dragging code did not distinguish the case of dragging the content of an input control
as a special case. The markup placed in the pasteboard included the style information.
I've modified the Clipboard class interface adding a new method writePlainText to match the
behavior of the copy and cut commands and modified the drag code to detect the special case.
I've modified all the platform specific implementations of the Clipboard class.
        
* dom/Clipboard.h: Added writePlainText pure virtual function.
* editing/Editor.cpp:
(WebCore::Editor::cut): Renamed nodeIsTextFormControl to isNodeInTextFormControl.
(WebCore::Editor::copy): Renamed nodeIsTextFormControl to isNodeInTextFormControl.
* editing/htmlediting.cpp:
(WebCore::isNodeInTextFormControl): Added, after removing the implementation with the old name
in Editor.cpp
* editing/htmlediting.h:
* page/DragController.cpp:
(WebCore::DragController::startDrag):
* platform/Pasteboard.h:
* platform/android/ClipboardAndroid.cpp:
(WebCore::ClipboardAndroid::writePlainText): Added.
* platform/android/ClipboardAndroid.h:
* platform/chromium/ClipboardChromium.cpp:
(WebCore::ClipboardChromium::writePlainText): Added.
* platform/chromium/ClipboardChromium.h:
* platform/gtk/ClipboardGtk.cpp:
(WebCore::ClipboardGtk::writePlainText): Added.
* platform/gtk/ClipboardGtk.h:
* platform/haiku/ClipboardHaiku.cpp:
(WebCore::ClipboardHaiku::writePlainText): Added.
* platform/haiku/ClipboardHaiku.h:
* platform/mac/ClipboardMac.h:
* platform/mac/ClipboardMac.mm:
(WebCore::ClipboardMac::writePlainText): Added.
* platform/mac/PasteboardMac.mm:
(WebCore::Pasteboard::writePlainText): Added helper function.
* platform/qt/ClipboardQt.cpp:
(WebCore::ClipboardQt::writePlainText): Added.
* platform/qt/ClipboardQt.h:
* platform/win/ClipboardWin.cpp:
(WebCore::ClipboardWin::writePlainText): Added.
* platform/win/ClipboardWin.h:

LayoutTests: 

* editing/pasteboard/drop-inputtext-acquires-style-expected.txt: Added.
* editing/pasteboard/drop-inputtext-acquires-style.html: Added.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@54368 268f45cc-cd09-0410-ab3c-d52691b4dbfc