https://bugs.webkit.org/show_bug.cgi?id=70172

Reviewed by Adam Barth.

Source/WebCore:

Add a webp image encoder for the chromium skia ports, add it to the canvas
element toDataURL() flow with support for an optional quality [0.0-1.0].
Use a webp compression method (3) that provides good speed and compression
performance for this image format, and works well for various input image
types: line-art, screen-shots, and photographic images.

Test: fast/canvas/canvas-toDataURL-webp.html

* WebCore.gypi:
* platform/chromium/MIMETypeRegistryChromium.cpp:
(WebCore::MIMETypeRegistry::isSupportedImageMIMETypeForEncoding):
* platform/graphics/skia/ImageBufferSkia.cpp:
(WebCore::ImageToDataURL):
* platform/image-encoders/skia/WEBPImageEncoder.cpp: Added.
(WebCore::writeOutput):
(WebCore::importPicture):
(WebCore::importPictureBGRA):
(WebCore::importPictureRGBA):
(WebCore::encodePixels):
(WebCore::WEBPImageEncoder::encode):
* platform/image-encoders/skia/WEBPImageEncoder.h: Added.

LayoutTests:

* fast/canvas/canvas-toDataURL-webp-expected.txt: Added.
* fast/canvas/canvas-toDataURL-webp.html: Added.
* platform/chromium/test_expectations.txt: skip test on MAC CPU-CG (CoreGraphics)
* platform/gtk/Skipped:
* platform/mac/Skipped:
* platform/qt/Skipped:
* platform/win/Skipped:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@99319 268f45cc-cd09-0410-ab3c-d52691b4dbfc