Bug 1273095 - initialize |mStride|. r=jrmuizel

MozReview-Commit-ID: ElpMyYLcy0M

--HG--
extra : rebase_source : 5a3405d3bbf47f0f6d26071d25c2810c205da195

gfx/layers/basic/BasicImages.cpp

@@ -35,6 +35,7 @@ public:
   BasicPlanarYCbCrImage(const gfx::IntSize& aScaleHint, gfxImageFormat aOffscreenFormat, BufferRecycleBin *aRecycleBin)
     : RecyclingPlanarYCbCrImage(aRecycleBin)
     , mScaleHint(aScaleHint)
+    , mStride(0)
     , mDelayedConversion(false)
   {
     SetOffscreenFormat(aOffscreenFormat);