https://bugs.webkit.org/show_bug.cgi?id=79712

Reviewed by Tony Chang.

Source/WebCore:

Per the spec, an empty string should be returned when there is no data for the given typestring.

Test: fast/events/dataTransfer-getData-returns-empty-string.html

* bindings/js/JSClipboardCustom.cpp:
* bindings/v8/custom/V8ClipboardCustom.cpp:
* dom/Clipboard.h:
(Clipboard):
* dom/Clipboard.idl:
* platform/blackberry/ClipboardBlackBerry.cpp:
(WebCore::ClipboardBlackBerry::getData):
* platform/blackberry/ClipboardBlackBerry.h:
(ClipboardBlackBerry):
* platform/chromium/ClipboardChromium.cpp:
(WebCore::ClipboardChromium::getData):
* platform/chromium/ClipboardChromium.h:
(ClipboardChromium):
* platform/efl/ClipboardEfl.cpp:
(WebCore::ClipboardEfl::getData):
* platform/efl/ClipboardEfl.h:
(ClipboardEfl):
* platform/gtk/ClipboardGtk.cpp:
(WebCore::ClipboardGtk::getData):
* platform/gtk/ClipboardGtk.h:
(ClipboardGtk):
* platform/mac/ClipboardMac.h:
(ClipboardMac):
* platform/mac/ClipboardMac.mm:
(WebCore::ClipboardMac::getData):
* platform/qt/ClipboardQt.cpp:
(WebCore::ClipboardQt::getData):
* platform/qt/ClipboardQt.h:
(ClipboardQt):
* platform/win/ClipboardUtilitiesWin.cpp:
(WebCore::getFullCFHTML):
(WebCore::getURL):
(WebCore::getPlainText):
(WebCore::getTextHTML):
(WebCore::getCFHTML):
(WebCore::fragmentFromHTML):
* platform/win/ClipboardUtilitiesWin.h:
(WebCore):
* platform/win/ClipboardWin.cpp:
(WebCore::ClipboardWin::getData):
* platform/win/ClipboardWin.h:
(ClipboardWin):
* platform/wx/ClipboardWx.cpp:
(WebCore::ClipboardWx::getData):
* platform/wx/ClipboardWx.h:
(ClipboardWx):

LayoutTests:

* fast/events/dataTransfer-getData-returns-empty-string-expected.txt: Added.
* fast/events/dataTransfer-getData-returns-empty-string.html: Added.
* http/tests/local/drag-over-remote-content-expected.txt:
* http/tests/security/drag-over-remote-content-iframe-expected.txt:
* http/tests/security/drag-over-remote-content-iframe.html:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@109176 268f45cc-cd09-0410-ab3c-d52691b4dbfc