[Mac] Disable canvas backing store scaling (HIGH_DPI_CANVAS)
https://bugs.webkit.org/show_bug.cgi?id=115310

Reviewed by Simon Fraser.

Source/JavaScriptCore:

Remove ENABLE_HIGH_DPI_CANVAS_macosx.

* Configurations/FeatureDefines.xcconfig:

Source/WebCore:

Disable the automatic pixel doubling in canvas backing stores on high
dpi devices. This will potentially make canvases look worse of high dpi
displays, but only if they were ignoring devicePixelRatio. Since the
majority of high dpi displays *do not* auto-double (including mobile
devices and other desktop browsers), this provides consistency and less
chance of unnecessary memory use.

* Configurations/FeatureDefines.xcconfig: Remove ENABLE_HIGH_DPI_CANVAS_macosx.

Source/WebKit/mac:

Remove ENABLE_HIGH_DPI_CANVAS_macosx.

* Configurations/FeatureDefines.xcconfig:

Source/WebKit2:

Remove ENABLE_HIGH_DPI_CANVAS_macosx.

* Configurations/FeatureDefines.xcconfig:

LayoutTests:

No need for platform-specific results any more.

* fast/canvas/2d.backingStorePixelRatio-expected.txt:
* fast/canvas/2d.imageDataHD-expected.txt:
* fast/canvas/canvas-resize-reset-pixelRatio-expected.txt:
* platform/win/fast/canvas/2d.backingStorePixelRatio-expected.txt: Removed.
* platform/win/fast/canvas/canvas-resize-reset-pixelRatio-expected.txt: Removed.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@149261 268f45cc-cd09-0410-ab3c-d52691b4dbfc