DRT and WRT should have HiDPI testing capabilities

Reviewed by Darin Adler.

Source/WebKit/mac: 

New method _backingScaleFactor matches SPI of a similar name that I added 
recently to WKPage in WebKit2. Equivalent functionality is needed for 
DumpRenderTree's HiDPI support.
* WebView/WebView.mm:
(-[WebView _backingScaleFactor]):
* WebView/WebViewPrivate.h:

Tools: 

New layoutTestController function setBackingScaleFactor takes a double for a scale 
factor and a callback function to call once the backing scale factor has 
successfully been set for the view.
* DumpRenderTree/LayoutTestController.cpp:
(setBackingScaleFactorCallback):
(LayoutTestController::staticFunctions):

On Mac, setBackingScaleFactor calls WebView _setCustomBackingScaleFactor. Other 
platforms do nothing.
* DumpRenderTree/LayoutTestController.h:
* DumpRenderTree/mac/LayoutTestControllerMac.mm:
(LayoutTestController::setBackingScaleFactor):
* DumpRenderTree/gtk/LayoutTestControllerGtk.cpp:
(LayoutTestController::setBackingScaleFactor):
* DumpRenderTree/win/LayoutTestControllerWin.cpp:
(LayoutTestController::setBackingScaleFactor):

Reset the backing scale factor by calling _setCutsomBackingScaleFactor with a 
value of 0, which resets to the system default.
* DumpRenderTree/mac/DumpRenderTree.mm:
(resetWebViewToConsistentStateBeforeTesting):

When generating the pixel dump, create a Bitmap of the appropriate size based on 
the backing scale factor. If it is a HiDPI view, paint into the context using 
displayRectIgnoringOpacity.
* DumpRenderTree/mac/PixelDumpSupportMac.mm:
(createBitmapContextFromWebView):

And now the same stuff for WK2. Again, new layoutTestController function 
setBackingScaleFactor takes a double for a scale factor and a callback function. 
* WebKitTestRunner/InjectedBundle/Bindings/LayoutTestController.idl:
* WebKitTestRunner/InjectedBundle/LayoutTestController.cpp:
(WTR::LayoutTestController::setBackingScaleFactor):
(WTR::LayoutTestController::callSetBackingScaleFactorCallback):
* WebKitTestRunner/InjectedBundle/LayoutTestController.h:

The InjectedBundle sends a message to the UI process to set the backing scale 
factor. It also processes a message the UI process will send back once it 
completes this task, and at that time, the InjectedBundle calls the callback.
* WebKitTestRunner/InjectedBundle/InjectedBundle.cpp:
(WTR::InjectedBundle::didReceiveMessage):
(WTR::InjectedBundle::postSetBackingScaleFactor):
* WebKitTestRunner/InjectedBundle/InjectedBundle.h:

Again, reset the backing scale factor by calling WKPageSetCustomBackingScaleFactor 
with a value of 0, which resets to the system default.
* WebKitTestRunner/TestController.cpp:
(WTR::TestController::resetStateToConsistentValues):

Upon receiving the SetBackingScaleFactor message, call 
WKPageSetCustomBackingScaleFactor to the given scale factor, and post a message 
back to InjectedBundle to say it has been done.
* WebKitTestRunner/TestInvocation.cpp:
(WTR::TestInvocation::didReceiveMessageFromInjectedBundle):
        
Don't use window snapshotting for the HiDPI tests. We don't have a way to fake a 
window's scale factor so we have to avoid that.
* WebKitTestRunner/cg/TestInvocationCG.cpp:
(WTR::TestInvocation::dumpPixelsAndCompareWithExpected):

LayoutTests: 

New HiDPI tests and results. These should be skipped on all non-Lion platforms.
* fast/hidpi: Added.
* fast/hidpi/broken-image-icon-hidpi.html: Added.
* fast/hidpi/broken-image-with-size-hidpi.html: Added.
* fast/hidpi/clip-text-in-hidpi.html: Added.
* fast/hidpi/resize-corner-hidpi.html: Added.
* fast/hidpi/video-controls-in-hidpi.html: Added.
* platform/gtk-wk2/Skipped:
* platform/gtk/Skipped:
* platform/mac-leopard/Skipped:
* platform/mac-snowleopard/Skipped:
* platform/mac/fast/hidpi: Added.
* platform/mac/fast/hidpi/broken-image-icon-hidpi-expected.png: Added.
* platform/mac/fast/hidpi/broken-image-icon-hidpi-expected.txt: Added.
* platform/mac/fast/hidpi/broken-image-with-size-hidpi-expected.png: Added.
* platform/mac/fast/hidpi/broken-image-with-size-hidpi-expected.txt: Added.
* platform/mac/fast/hidpi/clip-text-in-hidpi-expected.png: Added.
* platform/mac/fast/hidpi/clip-text-in-hidpi-expected.txt: Added.
* platform/mac/fast/hidpi/resize-corner-hidpi-expected.png: Added.
* platform/mac/fast/hidpi/resize-corner-hidpi-expected.txt: Added.
* platform/mac/fast/hidpi/video-controls-in-hidpi-expected.png: Added.
* platform/mac/fast/hidpi/video-controls-in-hidpi-expected.txt: Added.
* platform/qt-mac/Skipped:
* platform/qt-wk2/Skipped:
* platform/qt/Skipped:
* platform/win-wk2/Skipped:
* platform/win/Skipped:
* platform/wincairo/Skipped:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@97407 268f45cc-cd09-0410-ab3c-d52691b4dbfc