[Webkit-unassigned] [Bug 63305] New: [chromium] Divide by zero in TilingData

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=63305

           Summary: [chromium] Divide by zero in TilingData
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebCore Misc.
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: enne at google.com
                CC: jamesr at chromium.org, vangelis at chromium.org


There's a divide by zero showing up in Chromium crash reports: http://code.google.com/p/chromium/issues/detail?id=87153

This can only happen when there are no tiles because the layer size is zero.  I can see what could trigger this in code, but don't understand what state of events could cause this.  I'll upload a patch to prevent this crash, because we probably need that safety check anyway.

Callstack:

Thread 0 *CRASHED* ( EXCEPTION_INT_DIVIDE_BY_ZERO @ 0x610241a9 )
0x610241a9     [chrome.dll     - tilingdata.cpp:99]     WebCore::TilingData::tileBounds(int)
0x6102420c     [chrome.dll     - tilingdata.cpp:112]     WebCore::TilingData::tileBoundsWithBorder(int)
0x61032f95     [chrome.dll     - layertilerchromium.cpp:185]     WebCore::LayerTilerChromium::tileLayerRect(WebCore::LayerTilerChromium::Tile const *)
0x61032cc7     [chrome.dll     - layertilerchromium.cpp:117]     WebCore::LayerTilerChromium::createTile(int,int)
0x6103318e     [chrome.dll     - layertilerchromium.cpp:247]     WebCore::LayerTilerChromium::prepareToUpdate(WebCore::IntRect const &)
0x619dd6f3     [chrome.dll     - contentlayerchromium.cpp:115]     WebCore::ContentLayerChromium::paintContentsIfDirty(WebCore::IntRect const &)
0x61029b4b     [chrome.dll     - layerrendererchromium.cpp:430]     WebCore::LayerRendererChromium::paintLayerContents(WTF::Vector<WTF::RefPtr<WebCore::CCLayerImpl>,0> const &)
0x610298ff     [chrome.dll     - layerrendererchromium.cpp:328]     WebCore::LayerRendererChromium::updateLayers(WTF::Vector<WTF::RefPtr<WebCore::CCLayerImpl>,0> &)
0x61029650     [chrome.dll     - layerrendererchromium.cpp:239]     WebCore::LayerRendererChromium::updateAndDrawLayers()
0x611a04e2     [chrome.dll     - webviewimpl.cpp:2547]     WebKit::WebViewImpl::doComposite()
0x6119e02c     [chrome.dll     - webviewimpl.cpp:1148]     WebKit::WebViewImpl::composite(bool)

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