https://bugs.webkit.org/show_bug.cgi?id=102453

Patch by Yongjun Zhang <yongjun_zhang@apple.com> on 2013-03-29
Reviewed by Simon Fraser.

When we release an image(CGImageRef) from BitmapImage's cachedFrames, if the image was already
cached in subimage cache, it's ref count won't drop to 0 and the image won't be deleted.  Usually,
the subimage cache will clear the whole cache in a timer with 1 sec delay.  However, if WebCore has
to paint another subimage (not necessarily from the same CGImageRef) before this timer fires, we
will restart the timer and images inside the cache will stay longer than they should.

This patch does two things:
    - move SubimageCacheWithTimer and related helper struct into a separate file.
    - remove the image from subimage cache when we releasing the CGImageRef, this prevent subimage
cache holding the image after we released it.

No new tests, manually verified the CGImageRef is also removed from subimage cache
when we releasing the image from FrameData::clear.

* WebCore.vcproj/WebCore.vcproj:
* WebCore.xcodeproj/project.pbxproj:
* platform/graphics/cg/BitmapImageCG.cpp:
(WebCore::FrameData::clear): remove the image from subimage cache before we releasing it.
* platform/graphics/cg/GraphicsContextCG.cpp:
(WebCore):
(WebCore::GraphicsContext::drawNativeImage):
* platform/graphics/cg/SubimageCacheWithTimer.cpp: Added.
(WebCore):
(SubimageRequest):
(WebCore::SubimageRequest::SubimageRequest):
(WebCore::SubimageCacheAdder::hash):
(SubimageCacheAdder):
(WebCore::SubimageCacheAdder::equal):
(WebCore::SubimageCacheAdder::translate):
(WebCore::SubimageCacheWithTimer::SubimageCacheWithTimer):
(WebCore::SubimageCacheWithTimer::invalidateCacheTimerFired):
(WebCore::SubimageCacheWithTimer::getSubimage):
(WebCore::SubimageCacheWithTimer::clearImage):
(WebCore::subimageCache):
* platform/graphics/cg/SubimageCacheWithTimer.h: Added.
(WebCore):
(SubimageCacheWithTimer): Added a data member m_images to record which image and its subimages are cached.
(SubimageCacheEntry):
(SubimageCacheEntryTraits):
(WebCore::SubimageCacheWithTimer::SubimageCacheEntryTraits::isEmptyValue):
(WebCore::SubimageCacheWithTimer::SubimageCacheEntryTraits::constructDeletedValue):
(WebCore::SubimageCacheWithTimer::SubimageCacheEntryTraits::isDeletedValue):
(WebCore::SubimageCacheWithTimer::SubimageCacheHash::hash):
(WebCore::SubimageCacheWithTimer::SubimageCacheHash::equal):
(SubimageCacheHash):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@147265 268f45cc-cd09-0410-ab3c-d52691b4dbfc